Hesitation Problem on Acceleration. Please Advise...
I recently got my 94 ZR-1 back from the body shop (was hit relatively bad on the freeway). The car has 85,000 miles.
I thought everything was alright after not driving the car for over 2 months. But then when going to get on the freeway I matted down the gas in third gear (4:09's) and I had a complete hick up loss of pwer almost like the car wasn't getting enough fuel. Soon after, the service engine light came on (never happened before). During regular driving, lower RPM's the car seems to drive fine. The service engine light only comes on after I give the car enough gas to make this "stumble". The same thing happens each time, like when I am using all 32 valves it is not getting the fuel it needs. It starts to accelerate and then when it gets to a certain point it just stops.
I am thinking it may have something to do with the fuel pumps or vaccum lines. I think I only hear one pump running when I first turn the key on and not the one under the front headlight.
Can some of the ZR-1 experts please give their input. Thanks.
How does car idle? check map sensor vac line at back of plenum. Vac pump by headlight should come on when you first turn key and stop after several seconds. Will car rev hard to 7000rpm if not you need to check for code 61 this means it could be bad selinoid or bad actuator or somthing to do with secondary vac.
could be the line at the back of the MAP sensor blew off, has the car backfired recently? Could be injectors. To test this pull the plenum and put an ohm meeter on them. They should be between 12.5-13/
I am trying to think of something the body shop could have done to cause it loose power. The car does idle hugh sometimes around 1100-1200 rpm for a while when you come to a light but then usually comes down. I know the shop took off and put back on some vaccum lines. (High idle when I was down there and they started it up- over 2000 rpms)
Could only running on one fuel pump cause the symptoms I am talking about? I can not hear the fuel pump by the headlight (I know because I used to hear it) and now it doesn't make the same noise when I turn the key.
When I mat the pedal down the usually only revs till like 3000 before it stumbles with no power and then I let off (exactly like having not enough fuel).
The car has not backfired recently, just stumbles with no power. But under normal driving the car seems fine on power and everything else.
Would be comparable to driving with your key off (my chip has this car to be programmed to full power) all the time.
I don't think it is the injectors because they did not seem to affect the car before the accident.
Thanks for the help...I appreciate it.
FYI: The car was not doing any of this before the accident or the body shop and it would pull hard to 7000 with no stumbles.
Last edited by thomasguy6; 12-24-2005 at 04:16 PM.
If you read my first post I say it may be a secondary prob your the one that said gee go pull your plenum for no reason .
It's not that hard and I would rather be hands on when making a repair and beable to check one off another then working with the top of the motor on. someone needs to get some holiday cheer.
I am trying to think of something the body shop could have done to cause it loose power. The car does idle hugh sometimes around 1100-1200 rpm for a while when you come to a light but then usually comes down. I know the shop took off and put back on some vaccum lines. (High idle when I was down there and they started it up- over 2000 rpms)
Could only running on one fuel pump cause the symptoms I am talking about? I can not hear the fuel pump by the headlight (I know because I used to hear it) and now it doesn't make the same noise when I turn the key.
When I mat the pedal down the usually only revs till like 3000 before it stumbles with no power and then I let off (exactly like having not enough fuel).
The car has not nackfired recently, just stumbles with no power. But under normal driving the car seems fine on power and everything else.
Would be comparable to driving with your key off (my chip has this car to be programmed to full power) all the time.
I don't think it is the injectors because they did not seem to affect the car before the accident.
Thanks for the help...I appreciate it.
FYI: The car was not doing any of this before the accident or the body shop and it would pull hard to 7000 with no stumbles.
call them and ask if it backfired while they had it.
It's not that hard and I would rather be hands on when making a repair and beable to check one off another then working with the top of the motor on. someone needs to get some holiday cheer.
Why would you want to send someone strait out to pull plenum when it is not necassary yet I love waiting for plenum gaskets dont you
I think that I would start with whats simple. How old is the fuel filter? How about plugs and wires? Check the map sensor line at the rear of the plenum although, when mine blows off it runs crappy even at idle. If you want to check the vacuum lines under the plenum, disconect the vac. line near the oil filter and attach a vac. pump. Apply about 12 hg and see if it holds. Also, when you turn the ignition key to on that vac. pump up by the headlight should come on at least for a second or two. For the fuel pumps, you can attach a guage at the rail and turn the key on. Pressure should spike to about 52 psi, then drop to about 48 and slowly bleed off from there. You can also check them individually by pulling each fuse seperately and rechecking as stated above. One is in the normal fuse panel, the other is under the pass. side hush panel.
Good luck,
call them and ask if it backfired while they had it.
That's a good point, because the non-owner would tend to release the key before the motor is running, and this tends to be the cause of backfires when you go to start it again. They would not admit it or remember, but that hose is the first thing to check.
Location: No more yankee my wankee, the Donger is tired!
Quote:
Originally Posted by VetBoyZR1
That's a good point, because the non-owner would tend to release the key before the motor is running, and this tends to be the cause of backfires when you go to start it again. They would not admit it or remember, but that hose is the first thing to check.
It's not the Map Sensor hose. The car would be would have a horrible idle, it would be pouring black smoke out the back and the check engine light would be on immediately. His symptoms occurred while driving.
I would think that the first things to do would be to run car with power key off to try to eliminate the secondary system and also to pull the code. Checking the fuel pressure would be a next check using the service manual procedures. I had a problem similar that turned out to be the secondary injectors being bad. I also had the in line fuel filter plug that caused the car to stall. Good time to get the sevice manual out. I am not a mechanic, but I pulled my plenum and replaced the injectors so it is not that hard. Good luck, I hope it is something simple. Ron
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Hesitation Problem on Acceleration. Please Advise...
