A frightening experience....

[Guest Stephen Lyons]

I just had a very upsetting malfunction in my '88. I was driving around town for the first time in several months (I keep the battery disconnected but do start it once a month when it is not being used). On about my fifth trip into town today, I was coming up on a stop sign when the car didn't want to stop. At first I thought the brakes were failing, but I quickly realized what was happening was that the engine had begun racing, almost as if the accelerator was floored. I've experienced surging with modern cars before, even once before with this one, but this was the mother of all surges.

I got the car stopped & the engine shut down. After a few seconds, I restarted it, but it was still racing, so killed it again. After a few more moments, I restarted it once more, & it was fine.

Just an awfully scary thing, though, which could have very easily resulted in an accident. At the moment I don't trust this car very much, & my initial reaction after this severe an episode is to be rid of it altogether....

Has anyone else experienced a similar problem?

[Guest F14CRAZY]

Sounds like a bad throttle position sensor or something.

[Guest wally888]

Actual accelerator position when racing?

[Guest Stephen Lyons]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Actual accelerator position when racing? </div></div>

I had taken my foot off to apply the brakes....

[Guest wally888]

O.K., we know where your foot was (sorry, couldn't resist) but did the accelerator rise as you removed your foot?

[Guest Stephen Lyons]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">O.K., we know where your foot was (sorry, couldn't resist) but did the accelerator rise as you removed your foot? </div></div>

Well, I was a bit too busy to be looking down there to see, but I would emphasize that I been only driving along at about 25mph before this happened, & had probably been coasting for 100 feet or more when it suddenly took off as I described.

[Guest F14CRAZY]

Soak it all with WD40 or your favorite spray lube and call it good (the underhood linkages and under the dash)

[Guest Ranger]

Just a stab in the dark Stephen, but you said this has happened

with other modern cars, do you brake with your left foot?

[sahein]

Yes I have experienced this problem. Strange problem. I finally resolved it by loosening the screw that retains the return spring on the throttle body. Try loosening the screw maybe a turn and then check to see if throttle closes fully. Use locktite or something similar to retain the screw in position after loosening.

I posed something years before on worn throttle body acceleration problem.

[sahein]

Repost

Car coasts a long way --- Sticking throttle

#60555 - 04/10/02 02:22 PM

A while back I saw a post for a request for information on why his car was coasting for a long way. This may be due to a sticking throttle. If it sticks in a more open position at an inopertune time it may have bad concequences.

If the throttle is sticking it may be due to worn bushings. This problem can be temporarily remedied by slightly backing off the 12mm nut on the throttle shaft located under the black plate that holds the throttle linkage. If this is the problem, then normal spring tension should return.

To prevent the nut from backing off due to vibration if left in this position, the shaft should be double nutted or a drop of locktite or two could be used until the problem can be properly resolved.

[Serge]

Hello,

I've owned my 88 for about a month now. I've experienced this surge, although not racing like Stephen described. I'll be at a traffic light and for no reason I feel to car wanting to take off, I then apply the brakes a bit harder to hold the car back.

What causes this phenomena ?

Thanks

[Guest kennyw]

I would think the key to this problem is his statement. [& had probably been coasting for 100 feet or more when it suddenly took off as I described. ] So I would leave the sticking throttle plate out. It must be something electronic. My Reatta had always seemed to [drift] for a long time. One day while drifting I took my foot off the gas pedel and watched the rpm guage. The rpm droped very little and came down as the car speed came down. I would expect it to drop to idle speed but it didn't.....Some of you try this......ken

[Guest maybe2fast]

it could be a sticky IAC motor also. Just my $0.02

[padgett]

Sounds to me like a sticking IAC as well compunded by the DFCO (Decelleration Fuel Cut Off) which, despite its name, is the computer commanding a raised idle speed from the engine. While costing to a stop, pop the gear into neutral and feel what happens. I *think* we finally got it dialled out on Greg's car.

Now if while the engine is sending this command to the Idle Air Controller, the computer will keep increasing the command until something happens. This may be the IAC popping loose and opening way too far and then sticking again when the computer tries to throttle back.

If this is the problem then the cure is to clean the IAC (several posts on the subject).

In general, the idle speed command should never exceed 1500 rpm when cold. Hunting (idle speeding up and then slowing down) or occasional stalling whilke coming to a stop can usually be traced to a sticky IAC. A warm idle should be within 50 rpm of the target (625 rpm stock warm, mine are set to 700 rpm to improve stopped a/c performance) and should not vary more than 25-50 rpm.

I would not expect a worn throttle body problem to surface except at very high milage or if used entirely in stop and go traffic. If cleaning the IAC (have seen as low as 50,000 miles and sitting for months would aggravate) does not work then I would look into the throttle plate itself sticking but would check the IAC first.

[Guest Stephen Lyons]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Actual accelerator position when racing? </div></div>

I thought at first this and the subsequent queries about my foot position this were sort of a silly questions, but they in fact led to the solution. I will elaborate after first saying I offer an embarrassed aplology, & hope that at least someone else can learn from my idiocy.

You may recall I said I had not driven the car for awhile. Now I know from my experience with other Teves ABS equipped cars that under these conditions, the brake pedal is likely to be a little soft & prone to a bit move travel. This is because the accumulator, which is probably not up to specs on most of these older vehicles (the "fix" to get the brake pedal working properly again is to pump it 20-30 times with the ignition off, but that really just masks the fact that the accumulator is weakening).

Yesterday, I had the engine racing once again as I was applying the brakes. This time I looked down at the accelerator & realized that the brake pedal was depressed below the level of the accelerator & that I was just grazing the accelerator with my foot as well. Of course, the deeper I pressed the brake pedal, the faster the rpm's were, too. This is possible because of the way the Reatta accelerator pedal is flared out to the bottom & left. I will bet my prior occurences were due to the same circumstances, only just not as severe because the brake pedal was not going down so far.

I feel stupid about this, but had to come clean to the group....

[Guest wally888]

I have on ocassion had this happen however I think you should take a few minutes and give the Teves the tests!

[padgett]

Once drove one of the original Minis while wearing boots. Hit the clutch, brake, and accelerator at the same time with one foot.

[Guest Ranger]

The overlap of the brake/accelerator was what I was getting at when I asked if you were a left footed breaker. In my prior life, I did some accident reconstruction. In one of the cases, a driver was wearing large boots, the harder he pushed on the brake with his left foot, the harder the bottom of the brake pedal pushed on his right foot which was on the accelerator, lost a baby in a stroller on that one. The brake flush brought my spongy pedal up to what feels normal.

[Guest EDBS0]

I sometimes have the same problem. Big feet.

[Guest Greg Ross]

The DFCO Padgett referrs to is not that apparent with an Automatic tranny, drop in a manual tranny and it's quite something else. The ECM is obviously programmed to regulate the IAC relative to VSS signal(vehicle speed)If you drive an '88 or '89 you can watch this by going into Diagnostics and watching the IAC value. At speed your IAC will not drop back to idle + or- 20 when you come off the gas. It just hang up there, Padgett described this to me as GM's way of inducing less emmissions when coming off the pedal. I also believe there's a connection with the Cruise Control whether its' on or off. After installing my 5-Spd. and before we addressed this DFCO I found by touching the brake pedal (cruise disable) my rpms would drop back rather then motoring me along.

BTW Padgett, the IAC still hangs up there, just not as bad. eg; 60 mph/ idle clutch in 1800 + or - and drops off as you slow down.