Wasn't sure how to search on this in the archives. Not really sure how to describe it either. If anyone knows of an existing thread, please advise. I'll try to be as brief as possible ...

Driving back to work from lunch today, I noticed a hesitation in the engine. I've noticed it since I bought the car but today it was more pronounced. Over the last few weeks, when shifting gears for the first time of the day (mainly after a first to second shift), the car would buck and nose-dive like the motor cut out, then quickly recover. This problem, for the most part, seemed to go away after I started letting the car warm up for 5-10 minutes before taking off in it - but it still does it on occasion. Today, while climbing through the revs in 1st, 2nd and 3rd gears, it seemed like the engine was having trouble accelerating past, say, 3000 rpms. It would do it, but it acted like it was really struggling to do so, and I could feel a surge. The car was at normal operating temp (just past the first unmarked line on the temp gauge) and the outside temp was in the 60's (lots of sun, no humidity). Finally, at rest, the idle will dip QUICKLY from 900 to 700-600 then back to 900 rpms. Not sure if these are all related. Thought I'd post everything I'm experiencing that relates to interruption of engine output.

Damn, this is so hard to describe. It's one of those "you'd know it if you drove it" problems. Does any of this make sense?

I'm still learning this whole mechanic thing so I thought I'd ask the experts for suggestions on where to start. Does it sound like a "starved for gas" problem? Ignition? Computer? HELP!!!!!

How long has it been since you bought the car? (Have you done any kind of tune up since you bought it?)
Checked Plugs & Plug Wires?
Inspected the Coil Packs?

Also IAC may need to be cleaned/replaced.

Do you get the Service Engine Soon light?
If so, have you pulled the codes?

If you just bought the car, does the Service Engine light come on when you are starting the car?

The 87 4 cyl has a number of issues that could cause this. make sure there are no codes in the ECM before you start. Even if there are no codes run the car to full temp, stop, reset the ECM, then got for a drive. This clears the learned data which may be off over time.

first off, check the thing for vac leaks. espcially the TBI base, and the PCV elbow at the manifold end of the pipe. put a small clamp on that elbow to make sure it is staying sealed at all times. don't over tighten the clamp.

The base gasket on the 700 TBI also covers the idle air passage. It has a nasty habbit of colapsing into the passage decreasing it's flow. This can cause odd things.

The IAC in the 700 is prone to gumming up its shaft. It has to be replaced when this happens, there are only a few chemicals that will clean it good without damaging it. Unfortunatly they mostly are regulated or banned in the US. ((They are carcynogens or ozone depleaters.)) You can try alcohol but it's hart to dry it out without reforming a sticky film inside the motor.

If you have to replace the IAC you may as well get the rebuild kit and a TPS. Rebuilding the thing is easy, but time consuming. You will need several Torx bits, up to T30 to work on it. Make sure the gaskets you install match the ones you remove. the kit covers several slight variant of the 700 and has multiple base and middle gaskets.

Scott, I know it because I drive it. I have the EXACT same problem when the engine is cold except I have the v-6 5-speed. After about ten minutes it just goes away. I haven't figured it out yet, been too busy. I think with mine, that since the extra fuel is going in, there isn't enough air to go with it. Just a guess though.

Try letting the car get hot at idle see if your fan comes on. If it does not then your temp sensor for the fan is no good that sensor go,s to the ECM to set the timing (if we can call it that on dis motor) also it helps the ECM set the TPS. if the fan does come on then check your wires start with the number 1 wire frist if the wires look good try the coils its most likely one of the 3 I have a 1987 it did the same thing as your car I changed all 3 at the same time no more crazy idle. good look EDDIE

So far as I can tell, I have the same problem except for a few differences- I have an 84 2.5, an auto, and my car doesn't do that until it gets past the first mark in the temp gauge. It cuts out the worst if I'm accelerating froma stop at more than half-throttle, and open the throttle quick. If I open the throttle slowly it feels like one big flat spot from ~1500 to ~3000 revs. Replaced the TPS a while ago, cleaned the IAC, and have a new egr gasket. any ideas?
Thanks,
Mike

We have the same problem on our 87 4cyl, and I call it a lean surge. Since I've rebuilt the entire eng and knnow the damn thing pretty intimately, we came to theroize that the coolant plumbing to the bottom of the intake mainfold must be intact. it is programmed to run very lean, and the fuel air mix must hit that hot spot on the bottom of the intake manifold in order to atomize properly. it always runs better when its hot, and it requires proper warm up time.

Also also replace your 195 therostat for a 180 why I dont know but it works that I can tell you I think IT HELPS KEEP THE MOTOR TEMP MORE CONSISTENT ( THATS WHAT MY CARS DOC. TOLD ME ) HE,S COOL IF ASK HIM WHY HE DID SOMTHING HE ALWAYS TELLS ME SO I CAN UNDERSTAND. GOOD LUCK EDDIE

DJ - Brought the car home on 11/2. Changed the plugs about a week after that. Still learning the terms - what does IAC mean? The 'Service Engine Soon' light does not come on during the problem but does come on when the car is started.

Thanks to all for the suggestions!

IAC IDLE AIR CONTROLL VALVE

Runs Lean? I can't say for all years, and all PROMS but I can tell you the one I have in my 87SC4 always wants to run the mix at 14.6:1. That's just a tad rich being stoic is 14.7:1. ((You can only verify this info with an ECM scanner. It can be diferant from car to car depending on exactly which PROM is in the ECM.))

I've also found recently that if you change gas in the DIS motor it can really mess with the learned patterns in the SRAM. These are the ECM "learned" paterns based on actually running the motor they can vary in huge ways and variations are caused by all sorts of things. You can check for this one by either putting in the old gas brand/grade or by resetting the ECM with the engine warmed up and driving the car some after the reset.

Mine for example chokes when you punch it if you drop from 93 to 89 octane w/o clearing the ECM. (Both fuels from same gas station even.) Reset the ECM and it's fat dumb and happy untill you change to some other gas it hates. If you go from 89 to 93, at the same station, the thing doesn't care much. I've had odd problems across brand too, even at 92+ octain.

This wierd stuff even happens in carb motors. My old 2.3l ford motor hated some brand of gas no mater what the octane numbers are. Even some national brands. If I put in Merrit it ran like hell. put in WAWA, Exxon, or a couple others it ran like a scalded bat. Merrit and WAWA are both fairly cheap local/regional brands.

On the other hand, my 86 2.6l dodge caravan, it's a mitsubishi motor I think, will eat nearly anything you dump in. Some days I think that truck would run on pond scum if I put it in the tank.

Eddie,
I replace plugs,wires,distributor cap and rotor when I bought the car. Checked the spark plugs when I did a compression test (above 120 across all cylinders! I was amazed!) The ignition coil is good. I'm gonna check the timeing tomorrow. I think my distributor might be worn and has some play in it or something..

I don't know if the DIS motor has a Thermac in the air cleaner, but on those that do, colder weather will result in a flat spot before engine warms up if the system is not operating properly (door doesn't close at startup). And the door not opening causes problems too once the motor is hot.

DIS motors do not have Thermac.

Another thing you might want to consider...
The "brick" in you catalytic converter may have finally broken loose and is plugging up. If its been a while you can actually shoot a chunk out of the cat and lodge it into the muffler. If you haven't changed the cat in a while you may want to consider.

Sorry about the space...

I bought my 1987 SC last September. It has the automatic transmission. The car first ran great... then it started getting cold. During cold or rainy weather my car began hesitating violently during acceleration and was difficult to get in gear (engine stalled) until operating temperature was reached. Naturally I replaced the plugs and wires. This did not help. Perplexed, I checked the trouble codes... none were set. All sensors showed correct values. After a couple of weeks at the dealer, they eventually replaced most sensors and reprogrammed the ECM yet it still did not correct the problem. Fortunately, after all of this time and $, the car could be put into gear, so it did help the problem. To this day I have not figured it out. The only thing that I have done is placed a remote starter unit on the car and start it every morning at least 5 minutes before attempting to drive. Unfortunately this will not help you because you have the 5-spd. I have posted this to the fiero-list several times with no avail. Does anyone think it could be a cold start injector problem? Otherwise, I am beginning to think that they always run this poorly when cold...

Note: Do not put Bosch Platinum plugs in the L-4. If you do, you should check them about a week later. The ceramic surrounding the electrode was completely eaten in a couple of days.

When I replaced the alternator last week, I had the battery tested ... it tested bad (I don't have the sheet with me but it was something like 10 or 10.5 volts).

If the battery is less than 100%, would the fuel pump be starved for juice ... making it run at less than 100% ... thus not giving the engine all of the fuel it needs to run?

BTW, Idle Air Control Valve ..... thanks, Eddie!

[This message has been edited by Scott2M4 (edited 11-28-1999).]

I would say highly unlikely. Once the car starts up and is running it's basicly just using the alternator. Plus, I don't think the fuel pump uses very much juice. I haven't figured out why mine does that. Has to be something the 4 and 6 cyl have in common since both are doing it.

I had cold Idle problems with my 87SC4 last winter. including but not limited to intermitant code 45's.

Recently I rebuilt the TBI unit, meaning cleaning and installing new gaskets, and replaced the IAC.

I found 2 things wrong while doing this.

1. The IAC was gummy inside the motor. This can make the IAC lag a step when the ECM adjusts it. A 1-2 step lag can throw off the mix w/o setting any code, or just a 44 or 45.

2. The idle air bypass passage under the TBI was partly blocked by a colapsed TBI base gasket. The IAB passsage is machined into about a 120* arc under the TBI next to the main bore.

So far we've had mornings with frost on everything, and I've not gotten another 45 set yet.

If the Idle mixture is off or the IAC is slow, it can also cause the problems described above.

[This message has been edited by theogre (edited 11-29-1999).]