94 GMC Jimmy hesitation problem

I just got this Jimmy, it has the 4.3 vortec, it has a hesitation after stopping and trying to accelerate, but it seems after it gets the gas flowing it takes off, and also sometimes when you go to shut it off it wants to keep on running. The MAP sensor has been changed, and I believe 4 of the 6 plugs have been changed(found 2 new ac delco plugs in door) and when starting it has to turn over for about 4 or 5 seconds before it starts and seems a little rough then kinda smoothes out, idles fine though. Check engine light is on but havent got anywhere to pull the codes( can this be done like a camaro where you use a paper clip?) But once you get past that hesitant spot it runs fine, and I did kinda smell some gas fumes after starting it. I know the converter or exhaust is not restricted because it has the down pipe and a cherry bomb then another piece of pipe and thats it. Any suggestions? Thank you in advance

Yes jumper pin A & B and read codes and post back codes.
Then clear codes and recheck.

Run a fuel pressure check for lose of pressure.
Post back fuel pressure readings.

I would also get the other two plugs in it.

On running after shut off is the idle rpm high?
What is idle rpm?

codes were
12
33
35
43
45
after getting codes I tried starting it and it fired right up, runs rough at first then smoothes out was idleing what seems alittle higher than a normal idle but maybe becuae its cold

when the guy put the map sensor on and didnt reset the codes- would that affect it?

Yes codes should be cleared and recheck for what comes back.
Clear and post back if any coms back.

What was bad on old map sensor?

Make sure new map sensor has good vacumn tomit and is working good.

45 is rich exhaust that can be caused by map sensor or wiring or vacumn to it.

Post back any codes that come back after code clear.

I'm not sure what was bad on old map sensor, he just said he put a new one on

Clear codes and post back what codes back.
Watch the map voltage sensor reading to pcm.

I need to make a correction from my first post and I want to apologize for this- the MAF sensor was changed but I originally posted that the MAP sensor was the one that they changed- so MAP sensor has not been changed

I need to make a correction from my first post and I want to apologize for this- the MAF sensor was changed but I originally posted that the MAP sensor was the one that they changed- so MAP sensor has not been changed
No problem.
Clear codes and see if any come back.
If so post back code no.
And check that fuel pressure.
And post back fuel pressure readings,

a cold start misfire with that collection of codes and I'd be looking at the distributor for the problem.

I was just reading this and noticed it was a '94, most likely engine code W. This engine does not have a MAF sensor. As the others mentioned, i would be looking at the distributor and if that checks out, another problem area is the injector/regulator. A fuel pressure test would be a good start, as was mentioned too.

it has a new cap and button on it, every once in a while when driving I get a small gas smell and sometimes a small antifreeze smell

Also, it says the MAP sensor voltage is too high which would mean low vacum- and if there is no load or slight load(like taking off from a stop) until speed was achieed it would have high vacum- but if there is a vacum leak it would have low vacum at idel but making the sensor think there is no vacum( am I right so far?) and the reason I am posting this is because after you get a little speed it does not hesitate at all and after I drive to work( which is an hour away) and you stop and take off it doesnt hesitate, doesnt really start hard either, I went out yesterday and it fired right up. I havent done the feul pressure test yet because I dont have the guage or the money to buy one, Im going to advance auto today to have the codes rechecked and reset so I will repost them tonite

went to Autozone and they said they can check 96 and up

Use the paper clip method to get your codes, like MT mentioned.

If OBD 1
Jumper pin A & B turn on key and read codes on check engine light.

ok, cleared codes this morning and I have these codes now
23
35
43

You have never posted back your fuel pressure readings.
What are they?

Code 23 is intake air tempt sensor code.
35 idle speed problem.
43 knock sensor problem.

Have you got the air intake sensor pluged in?

Also you have never told us about your idle speed RPM?

To be able to help you we are going to need info

Im not sure where the idle air temperature sensor is, I have no way of getting the feul pressure readings, no gauges and dont have the money to buy them. Im not sure of the idle speed RPM's, but I can tell you when your idling you go about 20 mph

The air temp sensor is located on the rubber boot for the incoming air, at the throttle body. Make sure it is plugged in and not damaged, this sensor is easily damaged if your not carefull. This can cause a rich/lean/hesitating problem. After getting some more info and thinking about it, I tend to think you have a fuel problem, maybe a leak at the injector, or the regulator. You do need a fuel pressure guage to check. You could take the upper part of the intake off and check for washing, but you run the risk of breaking the upper intake gasket, and if money is short, then that would make your truck run real bad, if at all. Generally, when you remove the upper intake, its a good idea to just replace this gasket, it becomes brittle and cracks causing vaccuum leaks. As for the knock sensor, check your wiring and make sure its connected properly, if that checks out and the wire is not damaged/burned/broken, then your next option is to replace the sensor.

ok, just replaced the IAT sensor and Im down to one code now its 43 which is the knock sensor- my old IAT sensor was hollow, you could see right thru it and the end was pretty carboned up

How isthe fuel pressure doing?
Have you checked it and checked for fast leak down?
How is the idle doing?
How is the hesitation doing?

Have you cleared codes and look to see waht comes back?

yes I have cleared the codes and the only one that came back is 43
I havent got to test drive after installing new sensor so I will post those results tommaro evening, but it did seem to idle better sitting there and it did start right up
I havent got the fuel pressure checked yet, but it seems fine to me, before after starting the motor and giving it some gas it would, it would seem like it hesitates just giving it throttle, now it dont fter the new sensor so hopefully with some good luck it might be fixed

You are gaining.
Let us know how it goes.

I definatly will MT, I still may end up cleaning the IAC sensor since the IAT sensor was pretty black, but it does seem to have an improvement just sitting there running, and I should probally do some new plugs after it was running rich and cutting out or whatever it was doing, or what do you think, should I get new ones just to be on the safe side?

I would go a new set of AC Delco plugs.
It has been my experience when a plug get black gas fouled they are done for or hard to clean.
Check that fuel pressure and leak down for sure.
Let us know how it goes.
On the knock sensor code save it for last.
First thing on it is check the wiring and voltage to knock sensor or sensors.
Good Luck

knock sensor is the only thing left throwing a code, it did run a little better, didnt hesitate or cut out as much, but now it has a small surge

MT I have been thinking, I didnt have the surge until yesterday on the way home, which I drive an hour to work then an hour home, I replaced the IAT sensor on the 25th, just started it and let it run maybe 2 minutes and that was it, the intake hose and old sensor are pretty carboned up, when I was on my wayto work yesterday I had a cup of coffee and noticed what looked liked a bunch of carbon deposits(like in the intake hose) on the lid of my cup and is it possible that the EGR got clogged up from it? I never had this until I removed the intake hose and put in the new sensor. And also what if my EGR valve was stuck, would that cause the hesitation and slight back fire? Or maybe its no operating right, it hasnt throwed out any codes, when its cold it idles pretty good and now when it warms up, still doesnt idle right really, but I did read that an EGR valve can cause pinging so maybe thats why my knock sensor threw a code. And I also read it can cause a misfire which could be my hesitstion im getting? And also after getting ready to leave from work yesterday it had to roll over about 7 times to start, but in the mornings when you hit the key it fires up- just a thought

ok, just noticed this today, when I go out and start it and turn the heater on it dont blow nothing out but after it runs for 1-2 minutes it starts blowing, its like the vacum isnt strong enough to open the vent but as soon as it warms up it blows real good, would it have something to do with low vacum or something, I think its related to my hesitation somehow

ok, Im going to clean the EGR valve today, got a new PCV valve, clean the throttle body and intake hose, I was looking at the EGR valve and it looks like it has never been removed, but I think it is sticking at times and its not closing all the way. Sometimes after driving at high speeds and stopping it still runs great, then after a few stops it starts to run funny again, so Im hoping its just clogged and not moving the way it should, is there any certain way I should clean it, I bought a can of throttle body cleaner so I can remove the TB and spray it out really good and the IAC valve, will it hurt to spray the cleaner in the EGR valve or will it damage it?

ok, I got the IAC valve which was very dirty along with the butterfly cleaned up, cleaned out the hole where IAC goes, I stuffed a towel in by the butterfly and sprayed throttle body cleaner in the IAC hole, cleaned the MAF sensor, never got to EGR yet, gonna do that tommaro, now I got a question, I got the knock sensor code and was told to save it for last, well I had to pull off the plastic vortec cover cause I dropped my star bit and laying under the plastic was a connector laying there not hooked to anything, then on the drivers side between the last 2 plugs looks like a sensor- is this my knock sensor? If it is there is no wire hooked to it and I believe that is the wire I found hidden, but the plugs looks like it might be broke- can I buy a new connector and splice it in? Should I leave it unhooked? I know it is supposed to adjust the timing, I have my intake hose off but started it after cleaning those things and it does seem to be a bit better. Also the PCV valve is the passenger side, what is the valve on the drivers side in the valve pan? What does it do?

The thing on the driver's side between the plugs is the knock sensor. I would definitely reconnect it, even if you need to get a used connector from a junkyard.

Other than the IAC sensor, MAP sensor and TPS, the only wiring under the 'vortec' cover should be for the IMTV (the round thing in the middle of the upper plenum) unless the wiring was shoved up there to hold it out of the way.

that is where i found the wiring for the knock sensor hidden, what is the piece on the drivers side coming out of the valve pan?

well here what I got after today- one side of my EGR valve wasnt tight, you could see what looked like kinda burn marks on the gasket from like where exhaust was leaking out, but I took it off, cleaned it got a new gasket and put it back on, cleaned the IAC valve, seems to set there and run alot better from what I can tell, but still idles high, I never got the knock sensor hooked up yet, so I knew it would throw a code but I checked the codes anyways and got a 35 and 43- 35 being the IAC valve and I looked at the knock sensor plug and I just need a new of them. So I'm guessing I need a new IAC valve or can a parts store check these?

I test drove it today for about 30 miles, it will sit and idle great now, but it still has a small hesitation when taking off, nothing like it was though, it also surges while coasting with foot off the gas pedal

well yesterday it got really bad after waiting in line at McDonalds, it was idling really bad- almost dying(even in Neutral) but it didnt die, kinda heard a poping thru my cherry bomb- hesitated on take off and low rpm but it seems about the rpm range to get into 2nd gear, and if you give it the gas like getting on a highway it picks up and goes, was getting codes 35 and 43 well I replaced the IAC valve this morning and now Im only getting code 43 will the knock sensor not being hooked up cause this? It kinda has a lope when idling- and when I give it gas in park it kinda stumbles kinda like it dont wanna rev up but does and seems like a miss- maybe the plugs?

where can I buy a knock sensor plug(connector) also do you think a bad coil could cause my problem?

ok, I got the knock sensor connector(not installed yet) But I started the Jimmy when I got home, had to roll over a few times to start and kinda acted like it wasnt getting enough fuel to start then finally did, and after I shut it off the pump continued to run for about 5 to 8 seconds after it was shut off- is this normal? I know I should hear it when I turn the key on to start to get the pressure up, but this was after I turned the key off - weak pump?

well I pulled out the black round thing on the intake and it looks like the drivers side is pretty clean about middle of the intake, I guess this would be washing from the nut kit? I also discovered a stripped spark plug hole in the #2 plug

Proper testing before throwing parts at it.:sarcasmsign:

If you would run fuel pressure test it would show fuel leakage inside platinum on fast leak and also if you have fuel pressure problems.

If it is leaking fuel inside platinum with upper cover off prime up fuel pressure and look for leakage.

Post back what you see in there.

well it will be coming off anyway because of the stripped plug threads

well MT, the hole wasnt stripped- it had Bosch super plugs with a longer thread on it and 4 of the 6 were loose like that, put delco cr43ts's in today, 1 plug wire broke, took off the plenium and drivers side is full of gas, went to 3 different stores today to get new lines but no one carries them, all have to order them. I never took the old ones out, Im not sure what all I have to do to get them out, could you give some info on this please? I got it disconnected from the spider(where the funny clip is)

If it is the nut kit type fuel lines.
They have to have trhe steel fuel lines at back of intake taken lose to change them.
When you get new lines take a good look at them and you will see.

And prime up fuel pressure and make sure lines leaking or for sure where it is leaking.

Drop them Bosh plugs in trash can.

when I turned the key on, the gas was coming from where the lines come thru the intake, it has the 2 big steel lines, one with valve on it, that runs into the plenium and then turn to plastic, the bosch already hit the trash!

well I got the new lines on today, turned the key on a few times to check for leaks and didnt see any, although I thought I heard a spray type sound from the front on the passenger side, like where the injector clips on the intake, not sure but I put it all back together, put new plug wires on it and started it, idles good, revs good and I shut it off and tried to restart and it rolled over a bit then finally started. I didnt see any leaks from the regulator, still has a very small miss, and I also think I have a broken motor mount on the drivers side, is it hard to replace? Can I just jack up the motor some and remove the old and put the new one in? Would the hard start be from the computer relearning? I let it run for about 2 or 3 minutes and then tried to restart it

I also have some gas in the oil I believe too, so I dont want to drive it until I get that changed,

How would I go about cleaning my spider injectors? Could I take it off and maybe soak it in some sea foam or something. I replaced the return lines due to small leaks at the end opposite of the spider, I had a good bit of gas on the drivers side and there was just a couple small puddles on the regulator side, and I think I got some gas in my oil, kinda smells like it, but after changing the lines, it started good the first time, let it run a few minutes(I also turned the key on and off a few times before putting back together to check for leaks) but it started good and I let it run a few minutes then I turned it off and went to restart it and it had to roll over a few times to start, plugs are new AC's, new wires(duralast) didnt change cap and rotor