For the past several months I have noticed slight hesitation when accelerating from a stop. Generally, if I give it a lot of gas the car accelerates normally, but if I only give it a little I can hear and feel the engine hesitating (or surging). This wasn't particularly severe so I have been waiting for warmer weather to try to fix it.

Recently, however, the problem has become much worse. I would try to accelerate from a stop and even flooring the accelerator would not result in any change in rpms. The car would slowly move forward, but there would be no acceleration for several seconds until it would suddenly decide to go and then it would accelerate normally. To make matters worse, it is now frequently stalling (dying). There is generally no warning that a stall is imminent unless I am stopped at a light and then I can watch the idle fall from 600 rpms. It will not stall above 2000 rpms and the engine continues to feel strong.

The car is due for a 60K service so I have begun performing some of that maintenance. I changed the fuel filter which had no apparent effect. I pulled the spark plugs and they were fairly sooty which the Haynes manual says indicates that the fuel mixture is too rich. I changed the plugs this morning (replaced with the OEM NGK's). This seemed to help the hesitation, but it did not go away entirely. The car also stalled again several times. Generally when it stalls, I have a hard time starting the car again. The engine turns over, but the tach shows that the RPMs won't go above 200 or so and the engine quickly dies. The only way to get it to keep running is to floor it before it dies and keep revving it for a while. Usually this allows me to get it back into drive and moving again.

I suspect that the source of the problem may be the MAF sensor. However, I have checked it according to the procedure in the Haynes manual and it seems to be exhibiting normal behavior. The check engine light is not on, but I went ahead and pulled the codes and I got 0304 which indicates a faulty knock sensor. I realize that other problems can cause this code to be tripped, but I have checked the sensor with a multimeter according to the Haynes procedure and it measures infinite resistence. Yes, my multimeter can handle more than 10 million ohms (40 million, in fact).

I am at a total loss here. Any help would be greatly appreciated.

The car is an automatic 96 GXE with 122K miles.

 

Do you have any mods? If your ambient air temp sensor is danlging because of an aftermarket intake, it will do exactly as you say. Mine did, but I later moved the sensor next to to filter, and it runs like normal again.

 

My only mod is a K&N cone intake (pop charger). I have the ambient air temp sensor "dangling" right next to the intake itself. It is within about two inches of the intake near the strut tower. I haven't moved it since I got the intake three years ago. Any other ideas? I'll make sure the connections are good on the sensor just to be sure. Thanks for the reply.

 

That problem you have had happen to my car before, I replace ngk plugs and adjust the IAC (idle air control). The black screw next to the throttle body, clockwise to let more air in. If its not the iac than you so get a vaccum gauge and check for vaccum, while you at that you should check the fuel pressure. Don't trust that haynes manual., because I use if before and it never help me, it give you spec. only. Everytime I got a problem and try to fix it, that manual don't tell you the all the step. You should get a service manual from the dealer.

 

your Problem = Coil Packs

 

He's not getting the codes, nor is he stalling after 2krpms.

 

who does? In nearly 90% of cases one DOES NOT get codes for having deteriorated coil packs. Not until the coils cause SEVERE cylinder misfires that you actually get such code.

and WTF? Stalling after 2krpms? Who ever said one stalls with bad coil packs? I replaced three already, with about 8 month interval between the replacement of each and my Max never stalled after 2k rpm!

 

First of all, let me thank everyone for the responses. I checked and adjusted a couple of things this afternoon and I think I have resolved the problem.

The first thing I checked was the PCV valve, and vacuum was present (as expected). The second thing I checked was the TPS. It registered the correct linear increase in resistance as the throttle was opened. Finally, I decided to check the idle speed. I don't have an external tachometer as the Haynes manual suggests using, but I figured the one in the car should be adequate. So, I followed the procedure for checking the speed, and after disconnecting the TPS and revving the engine a couple of times the tach showed the car idling around 400 RPM. Needless to say this is well below spec. I used the adjustment screw (as suggested by 96'MAXSE) to increase the idle speed to between 600 and 700 RPM.

It took it out for 30 minutes of driving through a neighborhood with a lot of stop signs and I experienced no hesitation and it did not stall. Is the problem solved? Hopefully, but I won't be sure until I give it a more thorough workout.

One more thought. In my original post I mentioned how the problem became worse recently. What I failed to mention was that I had driven home to Denver (5200+ feet altitude) from school in central NY (500 feet). If I understand how the engine determines the idle speed, it should be lower at a significantly higher altitude because of the lower oxygen content of the atmosphere. As a result, the idle was just high enough in NY for me to notice only minor drivability problems, but when I came home the idle dropped some to the point where the engine could no longer function correctly.

 

hey Solo950 i got the almost the same problem with my car. i made a post a couple of days ago and nobody answered. the problem with my car is that it drives very well untill its fully warmed up then when i come to a stop it feels so slow, and it keeps stalling when i mesh down on the pedal from a stop as well as when the trans has to dowshift. i also changed the fuel filter and had no affect either, i looked at the spark plugs and they had a light white powder all over them. like BOSS said i could be the coil packs but not necessarly cuz you would really feel a misfire , the whole car shakes i hope that we can figure this out cuz it ****es me off

 

I took my car out for a much longer drive last night including some highway and city driving. The hesitation that I had been experiencing is 100% gone and it did not stall. I used to be able to hear the hesitation at WOT getting on the highway. Around 2500 RPMs I would hear the engine noise decrease and then it would quickly come back up. Last night I did 0-80 from a dead stop and it was a beautiful sound the whole way. My next fix is going to be that damn knock sensor to see if I can get some performance back. Anyway, I still think it is going to be a while before I am completely confident in the car again, but this problem really seems to be resolved.

In case it wasn't clear in my previous post, the change that seemed to fix the hesitation and stalling was adjusting the idle speed by turning the "idle adjustment screw" (illustration 16.8 on page 4-12 of the Haynes manual) counter-clockwise. I followed the procedure listed for adjusting the idle speed with the exception of not using an external tachometer. I just used the one in the car. As I mentioned, my idle speed was below 500 RPM and I brought it up to about 650.

I have an idea about why your car works great until it is warmed up. Someone feel free to correct me if my reasoning is wrong here. The engine idles at a higher speed until it is completely warmed up (the purpose being to help warm the engine up). As such, before your engine is warmed up the idle is high enough that the car does not have problems. However, as it warms up the idle gradually drops and eventually it reaches the point where it is too low for the engine to function properly. This is consistent with what happened in my car. It never died on me when the engine was cold. It would hesitate, though. Anyway, I think it would be a really good idea for you to check the idle speed using the procedure on page 4-12 of the Haynes manual. If you don't have a Haynes manual, you can get one at an auto parts store or Amazon for about $15. I hope this helps.

 

You stilling using that Haynes manual? if it help you, that great. when I had that problem, that fuccn max stall on me on I-95 at 60mph or more.
I check every thing, it took me 3 whole fuccn day to fix this problem.

By the way you a mechanic or tech or somthing?

 

hey Solo950 thanks for the advice im gonna get that manual the first thing in the morining.