six35

my 91 c2 sometimes idles fine, and sometimes jumps up and down. when driving very easy, with foot barely on the gas and shifting at 3000 rpm, there are no problems. as soon as i give it full throttle or close to that, the car has no power and barely creeps up in rpm.

first it just hesitated, now it got worse and worse. the engine had been rebuilt recently. when i replaced the plugs a few days ago, they all looked little lean but that was when the car was still running with only few hesitations.

it feels like the fuel pressure is just not there, so i was thinking, it could only be either pump or pressure regulator?

maybe someone can help me

AJKOK1

A bit of a long shot, but what has the weather been like ? I had a similar problem when it was wet, and it ended up being my O2 sensor ( located on the top of the Cat). Symptoms where a "bouncy" idle, and a loss of power every now and then. Bypassed the O2 sensor ( as i have a cat bypass) and the problem dissapeared.

Just a thought

Al.

GT9111

It could be your distributor belt.

bhensarl

I second GT9111, have you checked your dizzy belt?
Brian

six35

well, the engine was rebuilt because one onf the dist. belts tore, so it burned a hole in the piston. so all of the timining and distributor parts have been renewed.
when i talked to the tech that worked on the car, and explained him the problem, he told me it must be a fuel problem, not a spark problem.
when i checked the plugs, they all looked the same(little lean) so i ruled out, that just one of the injectors was not working. so i was thinking, it could only have to do with the main fuel supply, which should be the pump or the pressure regulator.
i just dont know, what the nezt step should be, should i just start replacing them? i don't want to spend money by replacing parts i dont need to.

six35

i replaced the o2 sensor, a couple month before the engine broke, so, since it was pretty new, i didn't think that it needed replacement. first it was like your problem, loss of power every now an then, but yesterday, as soon as i hit full throttle, the car would just not accelerate. so i don't think that the o2 could cause that much of a difference. or what do you think?

Eric Kessel

Have you checked for any air leaks on the intake?

Dunasso

Even with a massive air/vaccume leak you would still have full trottle capabilities. Given the symptoms you've described, there is a good possibility that you have a fuel related issue. However, it would be in your best interest to take it back to the repair shop. Let them run the neccessary tests to determine what the problem is. There is no need for you to pull your hair out trying guess at it.


Duncan

BGLeduc

Our cars seem to have a handful of similar symptoms, and an equally large handful of solutions that work for one user or another.

I too have had that problem, although it seems to have gone away. It would almost always occur at slow speed (30 MPH at most), going slightly downhill with little throttle. I would then put my foot down, and nothing...totally dead stick. Then when totally floored, it would wake up.

I think most of the threads I have read indicated that the issue related to problems with the airflow meter (dis-assemble and clean some of the contact area???).

But I have never done that service. The last change I made was to replace the O2 sensor. And that was done on advice from Adrian that after market O2 sensors (which I had) were not water proof, and when in heavy rain, I would get a very severe hesitation, unsteady idle...the car would be un-driveable for a bit, then I pull over, and all is well again. Definitely had that problem too.

The new O2 sensors thus far seems to have corrected this, and maybe the initial hesitation issue mentioned by the OP. Since he has a new O2, then I would maybe search for threads discussing the airflow meter service.

BGL

viperbob

I'd start by looking at the MAF sensor of the throttle position sensor since you already replaced the O2 sensor. If one of these is having a problem, the ECU may not be reacting properly to a false signal. The result would be as you describe. Drivability is OK if you kind of feed in throttle slowly. If you get on it quickly, the car will just sort of sit there until some of the other sensors react and tell the ecu that more air is coming in and to adjust fuel, timing etc.

BGLeduc

One more thought.....

There is a TSB regarding the airflow meter wiring harness. Apparently, the routing of the harness can causes some pretty severe idel issues as well. Its an easy fix, just a minor re-routing of some of the cables.

Not sure what the cut off date is for the factory to have made a change, but my '90 required this as well. The TSB can be found on ALLDATA, if you subscribe.

BGL

six35

i just checked the Throttle Position Sensor, and noticed that by moving the throttle away from its neutral position, it has a click, and on the other side of the throttle body is another sensor that could click, (i guess to sense full throttle) but under full throttle, it does not click...
...is it supposed to? if so, how can i adjust it?

thanks for any help

gilessav

I'd second the MAF sensor check. Look at the connector for corrosion or poor contact as my car displayed similar trends which went away for a while after a new 02 sensor/dist caps/belt, but returned to make the car almost undrivable on random occassions. My specialist had previous customers with MAF problems and simply by cleaning up the connector (and looking at the fault codes on the hammer) the problem has since seemingly gone (the car also got a 24k service at the same time). Of course when i gave the car over to him to diagnose the fault it drove perfectly everytime he tried it.

DaveK

It should click at full throttle. When I found that mine didn't, I adjusted it at the pedal end - you can feel around the back of the accelerator pedal and the cable is adjustable. It's fiddly - but I adjusted the pedal slightly higher so that the WOT contact (which is what you are talking about) was made.

However - this won't cause your problem. It might make marginal performance differences (I think it's supposed to tell the DME to ignore the air flow sensor readings) but it will not cause anything this severe.

Fens

I had my engine resealed and replaced the clutch, flywheel at the same time. Car developed a rough idle, and power loss as you decribed and when applying full power acceleration, it had a terrible loss of power with a head snapping power kick surge shortly afterwards. We went the O2 sensor, transmission sensor, distributor replacement route with no luck. Eventually found out the original coil were still installed. It appears that there had been an upgrade or notice out on them. Once replaced all was fine. Good luck trouble shooting, but I'd take a look at the coils as they can give good readings on the diagnostics and fail intermittently without a pattern.