98 Blazer backfires still, after tune up


timssail
08-08-2006, 01:28 PM
my wifes 98 Blazer backfires when I open the throttle and has a loss of power going up a hill. i just had the intake gasket replaced while in the shop for the missing engine, plus a tune up: plugs,wires, roator, and the thing still misses. The mehcanic said to take it to a dealer. any thoughts? He did not find any codes either.

Tim

Rmbodie
08-10-2006, 02:28 AM
If it is backfiring out the exhaust .numerous things could cause it . spark timing , valve not seating, cam timing chain worn , debri stuck in a valve from the gasket change , bent valve . The list could go on . Check ignition timing , check compression . A valve problem will show up on a compression test .
What level of mechanic is he . Shade tree , or a bonified shop ? Rob

Eslhockey92g
08-10-2006, 09:06 AM
I know when i did a rutine tune up, Plugs,wire cap, rotor........ I had the two plug wires backwards on the distributor. it would idle rough but if i would touch the gas it would sputter like crazy

MT-2500
08-10-2006, 02:02 PM
my wifes 98 Blazer backfires when I open the throttle and has a loss of power going up a hill. i just had the intake gasket replaced while in the shop for the missing engine, plus a tune up: plugs,wires, roator, and the thing still misses. The mehcanic said to take it to a dealer. any thoughts? He did not find any codes either.

Tim

A good mechanic with a good engine capable scanner and fuel pressure gauge should be able to spot the problem.
Lot more than pulling the codes to checking and finding the problem.
Check for engine miss and fuel pressure.
If the intake was off the cam retart may not be set right.
Here is some guide lines on fuel pressure testing.
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.
MT
Also some tips on finding a good repair shop.
Check around Ask around
Word of mouth.
Family friends coworkers neighbors business people and delivery people.
Mailmen and parcel delivery people get around and notice a lot of stuff.
Even a good parts house knows what shops are good and not good.
Chamber of commerce and better business bureau and city hall.
If you find a good referral to a repair shop go look them over and talk to them.
Look for a clean looking busy place with nice people running it.
Ask a few questions and ask about their qualifications and training.
Not all places have trained tech/mechanics.
If they do not find a place that does.
Even all dealers do not have all trained techs/mechanics.

Let us know how it goes.

timssail
08-15-2006, 07:50 AM
the 98 Blazer from hell is now at the dealer and has been for a week. They just took me for other 600.00 and the thing still pops right at the throttle body. they replaced the plenum gasket yesterday and nothing has changed. The original problem is the back fire, not the intake manifold, not the plenum gasket, not the plugs, not the wires, not the rotor cap, not the fuel filter, not the alternator, Not the fuel pump:pressure is steady. The dealer and the previous shop could not get any codes on this vehicle, but they are getting some feedback from the computer. The cat. converter may be plugged but the dealer says no he would able able to tell. We are baffled

MT-2500
08-15-2006, 08:51 AM
the 98 Blazer from hell is now at the dealer and has been for a week. They just took me for other 600.00 and the thing still pops right at the throttle body. they replaced the plenum gasket yesterday and nothing has changed. The original problem is the back fire, not the intake manifold, not the plenum gasket, not the plugs, not the wires, not the rotor cap, not the fuel filter, not the alternator, Not the fuel pump:pressure is steady. The dealer and the previous shop could not get any codes on this vehicle, but they are getting some feedback from the computer. The cat. converter may be plugged but the dealer says no he would able able to tell. We are baffled

600$ and no fix I would raise a lot Hell.
You are getting took man.
Tell them to give money back or take it some place that knows how to fix it on there dime.

Sounds like you need to find a better dealer.
What was the fuel pressure readings?
Did they check the cat for back pressure.
What kind of feed back are they getting from PCM?

Tip on going to the dealer
Ask that only a factory certified gasoline engine performance specialist work on your car.
Not all dealerships are concerned with how repairs are dispatched, and not all dealership techs bother to take advantage of the training offered by Factory(the vast majority of which is paid training). If the dealer is uncooperative, ask for your money back and call around for a dealer that will accommodate you.
MT

timssail
08-15-2006, 09:33 AM
the Blazer from Hell is now running. It was the mass air flow sensor, it should have been replaced first. The part did not act like it was malfunctioning when tested but when the part was changed with one from a 99 the truck ran fine. What an expensive lesson! I will tell them that I will pay for the parts they put in but not the labor for the parts that were not needed. We will see.

MT-2500
08-15-2006, 10:22 AM
the Blazer from Hell is now running. It was the mass air flow sensor, it should have been replaced first. The part did not act like it was malfunctioning when tested but when the part was changed with one from a 99 the truck ran fine. What an expensive lesson! I will tell them that I will pay for the parts they put in but not the labor for the parts that were not needed. We will see.


Right on get on there case.
And thanks for posting back how it went.
Any good tech with a good engine scanner could have spotted the MAF sensor problem even if it was not setting a code.
Fuel trim and several other things should have told them where to check.
Glad you got it fixed.
Did you have to find it yourself or did they finaly figure it out?
Are you using a aftermarket air filter like K&N if so.
You will need to watch it close and if a K&N go easy on the oil and keep the MAF sensor cleaned often.
Good Luck MT

timssail
08-15-2006, 12:20 PM
thanks for the good luck Wishes. I did not find this by my self but thought all along that is what it should be as it was an air fuel mix problem. Black smoke from the exhaust would usually mean that there was too much fuel and not enough air.

alblogg
08-16-2006, 06:14 PM
Right on get on there case.
And thanks for posting back how it went.
Any good tech with a good engine scanner could have spotted the MAF sensor problem even if it was not setting a code.
Fuel trim and several other things should have told them where to check.
Glad you got it fixed.
Did you have to find it yourself or did they finaly figure it out?
Are you using a aftermarket air filter like K&N if so.
You will need to watch it close and if a K&N go easy on the oil and keep the MAF sensor cleaned often.
Good Luck MT
About the K&N filter ever sence I put one on my '99 the engine lite comes on about every two three months and that one of the codes I get so I just reset it. Could I be getting the codes because the sensor needs cleanedmor to much oil?

MT-2500
08-16-2006, 09:09 PM
About the K&N filter ever sence I put one on my '99 the engine lite comes on about every two three months and that one of the codes I get so I just reset it. Could I be getting the codes because the sensor needs cleanedmor to much oil?

It would be better to start a new post on it.

Could be or could not be.
To start with you need to get the code no.
Also a good computer read out may tell you if engine fuel trim is running neg or positive.
How many miles on it and what is the tuneup history.
MT

alblogg
08-17-2006, 10:49 PM
It would be better to start a new post on it.

Could be or could not be.
To start with you need to get the code no.
Also a good computer read out may tell you if engine fuel trim is running neg or positive.
How many miles on it and what is the tuneup history.
MT
92000 and I have owned it a year and not tuned it up because it runs fine.

BlazerLT
08-17-2006, 11:43 PM
The plug wires on the driver's side are mismatched.

Anyone have the picture of the way they hookup?

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