Hesitation, staggering on acceleration and poor gas mileage.


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JoshBarber
03-20-2006, 01:52 PM
I did a search, but wanted to see if anyone currently on the board had any suggestions with this.

98 Chevy Blazer LT w/ 4whl Drive
Approx 120k miles

Last "tune up" (wires/plugs/cap/rotor) was less than a year ago.
Last fuel filter replacement was less then 4k miles ago

Ran a injector cleaner a week ago...with some, yet little improvement.
Vehicle still seems sluggish.

I had a feeling it was more of a sensor issue...something with MAS or MAP, but I have no warning lights, and the computer shows no error codes. I dont want to replace either for $100 + and find out its neither.

Any common issues that people have found and fixed?

JoshBarber
03-22-2006, 08:49 AM
Noone at all has any advice here?

MT-2500
03-22-2006, 09:52 AM
Well I will get you started.
What engine?
What kind of spark plugs? Air filter? Any missing?
How is that fuel pressure?
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

Pull plugs and have a look at them.
And double check that fuel filter.
Check for good hot blue spark to aall plugs.
Also if good fuel pressure and good ignition.
You may need to check that back pressure on the exhust system.
MT

JoshBarber
03-22-2006, 11:10 AM
I do have trouble cold starting. Usually takes the second time around.
I dont want to sound too stupid, but once I get a fuel pressure gauge, how do I connect it to check?
thanks
J

swalt
03-22-2006, 11:39 AM
Is it constant or intermittent? You mentioned all the basics that you replaced, but wires have been known to fail. If you say intermittent, are the outside conditions damp, or cold and the problem presents itself (staggering) after a few minutes of driving. Do you have problems after rain or a carwash?

JoshBarber
03-23-2006, 12:18 PM
intermittant......and I havent found any consistent conditions that contribute to or lessen the effect.

BlazerLT
03-23-2006, 12:23 PM
MAF sensor needs cleaning.

JoshBarber
03-23-2006, 12:56 PM
MAF is clean

MT-2500
03-23-2006, 01:02 PM
I do have trouble cold starting. Usually takes the second time around.
I dont want to sound too stupid, but once I get a fuel pressure gauge, how do I connect it to check?
thanks
J

There is a test port/adpter on your fuel rail.
A good type fuel pressure gauge will have the fittings to hook it up.
Even if no cold start problems you need to run a the full fuel pressure test.
It is the only way to seperated from a fuel problem or other.
Tape the fuel gauge to windshield or mirrow and have it on there when it does it.
MT

blazee
03-23-2006, 04:45 PM
Regardless of personal feelings and past behavior, personal attacks can not and will not be tolerated. I have removed all the inappropriate material from this thread. If this continues, I'll be forced to lock this thread.

BlazerLT
03-24-2006, 01:39 AM
I would still point the finger at a malfunctioning MAF sensor.

Most hesitation on tuned up engines is caused by it.

JoshBarber
03-24-2006, 08:46 AM
if both sides of the connection are clean, what more can you do other than replace it? I was trying to get a more definate answer before I dropped $100+ and realized it was still happening

MT-2500
03-24-2006, 09:45 AM
if both sides of the connection are clean, what more can you do other than replace it? I was trying to get a more definate answer before I dropped $100+ and realized it was still happening

A lot of times a good cleaning can help a MAF sensor.
Get some good quick dry electrical cleaner or the special MAT sensor cleaner and just spary the sensor wires inside it good. Do it at least twice spray and let dry and spray it again. No scrubbing or rubbing. Carb cleaner is it next best cleaner.
If you are running a K & N air filter go easy on the oil in it. The oil from them will get in MAF and air tempt sensors and throw them off. Or even road dust from a regular air filter will get dirt in a MAF sensor.
Clean it and see if it helps. Check fuel filter and fuel pressure to post back readings.
How is the spark plugs? How old and what kind? AC-delco?
MT

JoshBarber
03-24-2006, 10:57 AM
thanks MT.
Will spray it anyway just as an attempt. I would think it wouldve set off a check engine light if there was a problem with it though. will check the plugs also. replaced them not even a year ago with properly gapped AC Delco plugs.

swalt
03-24-2006, 11:08 AM
Josh, You mentioned you did an injector flush, but was this a fuel additive or did you have a professional flush done?

In the past, my mechanic has always done the fuel flush with the single can (IV setup) to the Shrader valve, got the truck running on the cleaner and then pulled the fuel pump relay to run the truck simply on the cleaner. His shop recently switched over to a 3 bottle system. Two bottles hang on the IV rack, one to the Shrader, one hose into the throttle body and a can in the tank afterwards. It does a full cleaning and takes about 30 minutes for the truck to go through the can. The throttle body attachment is like a small injector that sprays into the barrel as the truck idles. My throttle body and butterfly valve had quite a bit of carbon. After the cleaning, a nice bright aluminum/gold colour. Just a thought. I never realized how sluggish my truck felt until after having the system cleaned in this manner. Throttle response is like night and day.

MT-2500
03-24-2006, 11:34 AM
thanks MT.
Will spray it anyway just as an attempt. I would think it wouldve set off a check engine light if there was a problem with it though. will check the plugs also. replaced them not even a year ago with properly gapped AC Delco plugs.

You are welcome.
Give it a whirl and let us all know how it goes.
MT

BlazerLT
03-24-2006, 01:34 PM
I just hel;ped a guy over the phone with the exact same problem, he tried everything and then popped in a new MAF and everything was fine.

Remember, you can always take the MAF back after if it is not the cause.

JoshBarber
03-24-2006, 03:14 PM
where did you have this done Swalt?

and what would the cleaning be called?

swalt
03-24-2006, 04:39 PM
where did you have this done Swalt?

and what would the cleaning be called?

I'm in Toronto so you have a little ways to drive for an injector flush. The flush system is the BG Injector Flush.
http://www.bgfox.com/products.html?type=equip

blazes9395
03-24-2006, 10:13 PM
The best cleaner to use for this is brake cleaner. It evaporates and does not leave any residue on the sensor wires. Some carb cleaners have a lubricant in them to help keep things lubricated when you spray it. Electrical cleaner is good too, but I have always used brake cleaner and always had good results. But I agree with doing you fuel pressure check, and pressure leak down test, at least to rule them out.

Cloud Strife
03-24-2006, 10:14 PM
I had an injector flush done 2 years ago at the Dealership and it cured my hesitation problems.

I am just curious...........would the recommended 50/50 of Seafoam fix this?

JoshBarber
03-27-2006, 09:07 AM
swalt, and cloud -

just made an appointment for 11am today for a full flush at the dealership.
they said it includes a full internal flush for the injectors, and fuel lines, plus a cleaning of the throttle body and a fuel tank additive when theyre done. $129
Not exactly "cheap"....but it'll only take 45minutes total, so I can just go on my lunch break and get it done. I cleaned the MAF the other day with minimal improvment, so I'll post results on this after lunch.

AChatham
03-29-2006, 02:45 PM
How did it turn out?

JoshBarber
04-04-2006, 11:33 AM
those of you that know me, know I did a post about this a while ago.
I checked plugs, all of which looked fine. Nothing out of the ordinary. I changed the fuel filter (way ahead of its needed time), and had a fuel system cleaning done by the dealer to clean the lines and injectors.
Unfortunately, the surging and hesitation still exists. I found out today for a fact that wetness makes it MUCH worse. At slow speeds (i.e. - 1st gear) it sounds like its starving for fuel, and my other symptom is a longer starting time when the car has sat for a while.

I'm going to check the fuel pressure, as I assume this has to be the problem...I might bring it somewhere to have it checked...but I wondered if anyone had any suggestions, given the info just provided about rainy days making the problem MUCH worse.

Sound like a vacuum leak somewhere? Anyone had similar problem with fuel?

muzzy1maniac
04-04-2006, 12:47 PM
PLUG WIRES!!!! Or cap and rotor! I'd put money on it! Check tonight in the dark - take a spray bottle with water in it and mist your wires while the engine is running. I bet you'll see them arcing. I had this problem with cheap wires but even age and wear can cause it. Moisture usually only affects electrical issues and not fuel pressure. I think you can spray the wires with WD-40 or silicone spray to dry them off to get you to the store if need be.

blazee
04-04-2006, 12:56 PM
PLUG WIRES!!!! Or cap and rotor! I'd put money on it! Check tonight in the dark - take a spray bottle with water in it and mist your wires while the engine is running. I bet you'll see them arcing. I had this problem with cheap wires but even age and wear can cause it. Moisture usually only affects electrical issues and not fuel pressure. I think you can spray the wires with WD-40 or silicone spray to dry them off to get you to the store if need be.

I agree. That was the first thing that I thought of, too.

JoshBarber
04-04-2006, 07:03 PM
I changed them about a year ago. Plugs, Wires, Cap and Rotor. They're Bosche wires. Seems unlikely that they'd be the cause this soon.
Im still thinking its a fuel issue. Never felt a car surge the way this does in only low gear and had it be an electrical problem. Especially with the everpresent starting delay. Seems to me like its not getting enough gas at low speeds and when you step on it, its enough pressure once you get up to speed to keep pressure built up.
But I can try what you're saying. Thanks for the the suggestion.

muzzy1maniac
04-04-2006, 07:33 PM
If it is your wires... You're feeling less problem at higher speed because the truck is actually working less than when you're accelerating to speed. I've had bad wires out of the box. Besides remember K.I.S.S!

JoshBarber
04-04-2006, 08:04 PM
K.i.s.s. ????

blazee
04-04-2006, 08:08 PM
K.i.s.s. ????
A famous band:
http://www.kissonline.com/news/images/1_kjpn.jpg












j/k
It means "Keep It Simple Stupid" or "Keep It Super Simple"

JoshBarber
04-04-2006, 08:12 PM
yea yea. I got it. if I had to guess I'd say its 10 to 1 a fuel issue. but I'll go out in a few and spray the wires and report back

JoshBarber
04-04-2006, 08:54 PM
ok did it.
I DID in fact seem some slight arcing.
One where a wire ran against a cooling hose, and the most obvious being the COIL wire...both on the wire, and at the engine connection.
I felt slight hesitation when I drove it like that, although I would think it would have been much more extreme given how bad it was today, and how much more I just soaked them looking for the ARC.

MUZZY and BLAZEE:
You said you had the problem before...have either of you had this issue, and the symptom was what I'm having? A surging on acceleration that feels like the car is almost studdering? Also, is there any chance that it'd be caused by some sort of vacuum leak?

muzzy1maniac
04-05-2006, 12:30 PM
ok did it.
I DID in fact seem some slight arcing.
One where a wire ran against a cooling hose, and the most obvious being the COIL wire...both on the wire, and at the engine connection.
I felt slight hesitation when I drove it like that, although I would think it would have been much more extreme given how bad it was today, and how much more I just soaked them looking for the ARC.

MUZZY and BLAZEE:
You said you had the problem before...have either of you had this issue, and the symptom was what I'm having? A surging on acceleration that feels like the car is almost studdering? Also, is there any chance that it'd be caused by some sort of vacuum leak?

I had your exact symptoms that's why I was so sure it was the wires. Studdering is exactly what's happening. You're tyying to accelerate the truck is trying to accelerate by firing the plugs faster but the arcing is grounding the plug or plugs out so you're truck is studdering. Could there be other issues? Of course it's a Blazer - like the weather, if nothing is wrong wait 15 minutes. You saw arcing so there is your KISS problem. Replace the wires then see how she runs.

JoshBarber
04-06-2006, 07:37 AM
will do, they're bosches, so I think I have a warranty anyway

JoshBarber
04-06-2006, 01:28 PM
Just replaced the wires, I'll report back if the problem disappears or reappears.

swalt
04-06-2006, 10:19 PM
I put a post up here a couple days ago with a similar problem. Thought it was the cap when in fact it was the cap housing cracked where it screws in. My problem would only happen after a few minutes of driving on a cool morning, assuming condensation was building up inside the cap as the engine warmed up.

JoshBarber
04-07-2006, 07:36 AM
thanks Swalt, I'll keep my eye on the cap and rotor next if the problem persists....its fairly moist this morning, and will rain in my area this afternoon. its a good test day.

JoshBarber
04-09-2006, 07:23 PM
ok...heres the current situation.....

replaced the wires, and although it hasnt surged since, I'm not completely sure it fixed the problem...

BUT..I now have an additional problem since changing the wires. My gas mileage is HORRIBLE. Running through a tank in almost a day of regular driving. All I can think of is that I damaged a plug, or the cap and rotor during the wire change. Im not really noticing a rough idle, but...

Anyone have any other suggestions? Should I have reset the computer after changing the wires? HELP!

JoshBarber
04-10-2006, 06:49 AM
ok...heres the current situation.....

was having an arcing issue with 1yr old Bosch wires.
replaced the wires, and although it hasnt surged since, I'm not completely sure it fixed the problem...

BUT..I now have an additional problem since changing the wires. My gas mileage is HORRIBLE. Running through a tank in almost a day of regular driving. All I can think of is that I damaged a plug, or the cap and rotor during the wire change. Im not really noticing a rough idle, but...

Anyone have any other suggestions? Should I have reset the computer after changing the wires? HELP!

JoshBarber
04-10-2006, 08:07 AM
also I plan on replacing the fuel filter tonight...although I seriously doubt it caused this sudden drop in gas mileage. Would lean more towards whatever is causing it the hard start when its been sitting

DINO55
04-10-2006, 08:42 AM
JOSH, Just alot of Two Cent's here????

What year is it? 4wd or 2wd?
What Brand of Sparkplugs are you running in it right now? How old?
When was the last time you changed the cap and rotor?
Air filter is how old?
PCV Valve is how old?
Sticky Brakes possible?
Dirty injectors?
You mentioned Fuel filter already.
I belive that the gasoline we are using is still the winter blend (SHITTY)
Tire pressure OK?
Does your Fan blade spin freely?
Transmission fluid clean and full?

JoshBarber
04-10-2006, 08:49 AM
JOSH, Just alot of Two Cent's here????

What year is it? 4wd or 2wd?
What Brand of Sparkplugs are you running in it right now? How old?
When was the last time you changed the cap and rotor?
Air filter is how old?
PCV Valve is how old?
Sticky Brakes possible?
Dirty injectors?
You mentioned Fuel filter already.
I belive that the gasoline we are using is still the winter blend (SHITTY)
Tire pressure OK?
Does your Fan blade spin freely?
Transmission fluid clean and full?

1998 Chevy Blazer LT (4wd)
AC Delco's replaced last March 05 (basically a year old)
Changed wires/cap and rotor at that same time
Air Filter in Feb. of 05 (K&N was checked and is still clean)
PCV Valve was changed in March 05
Brakes seem fine
Just had a full fuel system cleaning done by dealer.
(yes fuel filter is fairly new but will change it anyway tonight)
Tire Pressure fine, no recent changes in it
Fan blade spins freely
Trans. Fluid is clean, but I do have a slow tranny leak at the radiator.
(I have added some occasionally so I beleive its full...why do you ask?)

muddog321
04-10-2006, 10:22 AM
Clean the MAFS in the air intake. See if that helps. Front O2 sensor could cause this but shiould see a SES light and have a code.

JoshBarber
04-10-2006, 11:25 AM
Clean the MAFS in the air intake. See if that helps. Front O2 sensor could cause this but shiould see a SES light and have a code.


hey muddog...thanks. I did this less than a week ago trying to solve the hesitation problem....but saw no change. The gas mileage issue just started.

JoshBarber
04-10-2006, 12:00 PM
What is the one electrical CONNECTOR that runs into the distributer cap?

JoshBarber
04-10-2006, 12:21 PM
I know this is blurry...but...

although it was changed out less than a year ago, I just pulled the PCV to check it out as well. rattles freely-allowing flow one way only...which I know is the main function....but it shows signs of what looks like burnt fuel (brownish buildup). Just wanted to ask if thats normal or a sign of any other issue?

http://i16.photobucket.com/albums/b40/JoshB_/pcv.jpg

534BC
04-11-2006, 02:40 AM
A couple more questions to help us help you if you don't mind.

what was the mpg before ? and for how long?
what is the current mpg ? and for how long?

JoshBarber
04-11-2006, 12:15 PM
A couple more questions to help us help you if you don't mind.

what was the mpg before ? and for how long?
what is the current mpg ? and for how long?

I dont know to be honest. It was pretty much average for most Blazer owners before...and its dropped a HUGE amount all of a sudden.

Lovedb4ever3
04-11-2006, 01:25 PM
anytime u change wires for a misfire your gonna wanna chane the plugs too because the longer they r not being fired the more fouled they r getting. Im sure some are fouled out pretty badly by now and they wont clear up with everyday driving.

Teal95Jimmy
04-11-2006, 01:43 PM
Are you driving with the A/C going or the front defroster or blend on. Using that with the air temp being above 40 degrees F will cause the air conditioning compressor to kick on.

AC compressor on=more load=more gas to do same amount of driving

Check under the hood anyway, there might be a sticky switch or relay that's keeping the compressor going.

Teal95Jimmy
04-11-2006, 01:46 PM
Also where you getting your gas? Have you changed brands lately? Some stations are now using a blend of gasoline and ethanol. Dont know if that will help or hurt mileage, mine doesnt like the 10% ethanol blend.

JoshBarber
04-11-2006, 02:25 PM
anytime u change wires for a misfire your gonna wanna chane the plugs too because the longer they r not being fired the more fouled they r getting. Im sure some are fouled out pretty badly by now and they wont clear up with everyday driving.

does anyone agree with this?

Cloud Strife
04-11-2006, 03:35 PM
Is your poor mileage over just one tank of gas? Because it is possible you could have gotten a poor batch from that Gas Station. Try a different one like Sunoco, Shell, Exon. Those are usually the higher quality stations at least in my area. The local SuperAmerica is causing horendous mileage on several family members cars. They are averages 50MPG lower.

They should be changing over to summer grade here shortly, but we have to wait for the Winter Grade to dry up first.

MT-2500
04-11-2006, 03:51 PM
also I plan on replacing the fuel filter tonight...although I seriously doubt it caused this sudden drop in gas mileage. Would lean more towards whatever is causing it the hard start when its been sitting

If you are having a hard start cold.
Here is one thing to check but the fuel pressure specs will depend on year and engine and engine code. Which you have not gave us. Post them back.
MT

Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

534BC
04-12-2006, 11:20 AM
somewhat agree.

I would do the cap, rotor, wires and plugs all at the same time if they were being changed because they were very old and had high miles.

If not then I would disagree and only change the bad component.

534BC
04-12-2006, 11:23 AM
My symptoms are a bit like yours, but very intermittent and light. It seems to be worse when it is wet , cold, or when all the lights, fans are on.

I can't remember where, but vagualy remember something about unhookling alternator and testing injectors with lower voltage.. I wish I could remember, because My problem is nearly non-existant with no lights on.

JoshBarber
04-12-2006, 11:31 AM
they werent being changed due to old age. they're about one year old. which is pretty new in my opinion. I changed them out because I saw the ARCing.

Unfortunately, the surge problem pursists. Any suggestions let me know.
Im starting to really lean towards believing its a fuel pump or pressure leak as I said before. Hard start after it sits persists as well.

muzzy1maniac
04-12-2006, 12:06 PM
Josh,

Where exactly was the arcing?

JoshBarber
04-12-2006, 12:20 PM
Josh,

Where exactly was the arcing?


Hey Muzzy -

Re-read post #9

JoshBarber
04-12-2006, 02:06 PM
How did it turn out?


This DID NOT solve the problem......search continues

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