Runs perfect.... until it doesn’t.

[Sfbradburn]

Hello all,

My brother in law gifted me a 1991 Festiva yesterday as a birthday present. 4speed, fuel injected. He hasn’t had time to mess with it and knows I’ve wanted one since like high school. Overall it looks and runs good except for one issue. I’ve spent the last few days searching the forum for this problem and haven't actually found anybody that has posted about it.

The car starts and idles fine cold and warm. Initially it drives fine cold and warm. But about as soon as it hits ~3000rpm it begins sputtering and lurching... let off the gas a little and it runs fine. I was able to cruise around 55-58mph without an issue, that little extra push to get 60, and it’d start dogging.

Brother in law and previous owner have replaced a lot under the hood, I’m working on getting a detailed list of what was done. Vacuum lines look new, plugs are new... I’ve made a list of possible things to check, but haven’t got under it yet. If there’s an obvious solution that someone wants to shout out I’ll give it a try.

appreciate any input!

[frogman]

Welcome to a Great forum. I am surprised that nobody has got back to you yet. I am in a bit of a hurry right now. Off the top of my head, I'd say check the fuel filter. Will it rev and hold 3000 rpm + in neutral?

[WmWatt]

Happy birthday. This may not be specific to the Festiva. A search of the Internet on missfire at high rpm's or similar might offer some insight.

[Sfbradburn]

Frogman, thanks for the reply! Brother in law had the fuel pressure checked, and was fine. I’m assuming that’s what changing the filter would attempt to fix if pressure was a problem? Not sure about idling and hitting 3000rpm, I’ll check today.

WmWatt, thanks! I took your advise and have been looking up the problem in general, not just with festivas.

To specify the issue a bit more, the problem happens gradually.. meaning when the engine is cold, I can jump on the highway at 4000+rpm and be going over 70mph no problem. As it’s reaching operating temperature, it will start that missing/bogging first around 4000Rpm, and then lower and lower as it gets hotter and hotter until it seemed to stay around 3000rpm as the missing point.

right after I made the initial post, I read about how exhaust back pressure can build as the vehicle gets warmer, and as your rpm’s increase. So I disconnected the Cat, and ran it without exhaust to see if there was any change. It may have delayed the heating process some... but once hot, I was skipping just as before.

I’m next going to check the idle control valve, and the wiring for it. From what I understand , it opens and closes with the heating of the engine so I figure it could be an issue if it’s not adjusting correctly. Where does it pull it’s temperature readings from? I’m assuming there’s a temperature sensor connected to it somewhere, so I’ll make sure the wiring is good on that too.

thanks.

[Sfbradburn]

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[WmWatt]

Perhaps the ignition control module? They are heat sensitive and near the end of their life they can act up when warm causing missing and stalling. Once the engine cools down they are normal again. The ignition control module used to be called transistorized points. On most Festivas they are bolted on under the distributor cap but were mounted on the fender or firewall for a couple of years in an attempt to keep them cool.

[Sfbradburn]

Frogman, So ran it again yesterday to test it in idle while hot. While driving around getting it to temperature, I noticed that it was skipping/missing at 3000rpm in 4th gear, and skipping/missing around 3800rpm. Once hot, it would rev passed 5000rpm before it started skipping.

So other vehicles I’ve had will display a blinking check engine light while there’s an ongoing missfire. Is that the case with a Festiva? Because it’s never blinked like that. But the light did pop up for the first time, so I’ll need to check that out.

[Sfbradburn]

WmWatt, didn’t see my ignition control module when I initially was looking for it yesterday. I’ll look again sometime today or tomorrow. I may try wrapping it in insulation tape to keep it cooler for longer. Used to do that to fuel components on my cherokee when it was getting heat soak.

[WmWatt]

I haven't read about the symptoms you are getting before. The cause could be mechanical or electrical. A couple of things you can do to look for electrical problems are first, run the engine at idle after dark and lift the hood to look for sparking, secondly try a vacuum guage whose needle will flutter if the ignition is missing. There is a permanent post about vacuum guages near the top of this page. Both of those techniques are cheap and easy. I've used both.

[1990new]

You say it's a 1991 efi 4 speed. So I'm assuming that the 5 speed transmission that came in the car when it was new broke at some point and it was replaced with a 4 speed? Is that correct?

I'm not a transmission expert but someone in the know might chime in here and give us your input on the matter. Would the fact that there there is no 5th gear in the car but the computer expect there to be, have anything to do with this? Probably not an issue since you describer the engine skipping when reving and not in gear.

Even if you think the vacuum lines look new, you still could have a vacuum leak somewhere.. you might want to take a closer look.

Do you know if the timing belt has been replaced in the last couple of years. If it has and the crank pulley was not tightened properly and thread lock applied, the keyway on the crank could be wallowing out causing the timing to change at different speeds and torque.

Just throwing a few more things out to think about checking.

[w4rkry]

The Festiva trans doesn't talk to the ECU, so It won't run any differently with a 4spd vs a 5spd

[william]

Check that your afm door is swinging freely. Also check for cracking or splits in the intake tubing. Had one do something similar right after I got it ,it had sat for a long time turned out to have a mouse nest in the air box. Also the timing was off due to a bent alignment pin on the cam. So you may check into the timing as well.

[Sfbradburn]

Thanks for all the suggestions! I havn’t had much time to fiddle with the car due work and having to run a lot of errands, but I did take the Festiva on a few trips and noticed a couple of differences that might help narrow down the problem.

Yesterday I needed to run to another town 50minutes away and decided to take the Festiva since I hadn’t gone longer than a 25ish minutes in it before. It was about 84 degrees out... There and back it ran like it had before, getting rough around 3000rpm, and maybe a little sooner a few times @2800rpm. Today I had to do a quick trip to town just over 20minutes away but it’s 90 degrees now. The Festiva eventually started running rough/skipping super early at like 2,500rpm. It got to a point where it started bogging at 2400rpm and loosing speed, and even when I took the car out of gear and gave it gas, it still wouldn’t rev passed 2500rpm... a couple of taps the floor and the thing back backfired super loud. Pretty sure I was smelling fuel at the time too, probably super lean exhaust. Anyways, if I coasted for like 10 seconds and let the engine idle down, it would run fine again until it got hot again I guess.


WmWatt, the wiring looks super sketchy in the engine bay, so wouldn’t be surprised if it’s sparking somewhere. I’ll check it out tonight. Definitely wanting to check the vacuum system as well.

1990new, so this model only came with a 4speed? It wouldn’t surprise me if that was the case, because I have a 5speed ball and only 4 gears lol. I’ll definitely look more closely at the vacuum lines, definitely seems like they could be the issue from what I’ve seen. Not positive if the timing belt has changed, but I’m assume it has at some point so I’ll put that keyway on the list of things to check.

William, AFM door is one of the top things on the list to check. I’ll let you know what I find. The bent alignment pin, was it constantly out of time or would it intermittently go out of timing?

This last trip made me thing there’s something somewhere that’s closing off the air when it’s hot, causing a super lean Mixture. Any Specific vacuum lines that effect the air-fuel ratio? Was also wondering if the bypass air valve could cause an issue on the highway when hot, I think I saw 1990new say in another thread that it opens or closes a door at 140degrees? Maybe that door is Or isn’t getting shut and closed depending on the rpm’s and heat.

Thanks everybody!

[WmWatt]

I know from experience if the temperature sensor is not working (voltage out of range) the check engine light will come on and go off again when it is back in range and store the code in the computer memory until it is erased. Stored codes can be read with a simple procedure. When you turn on the igntion the check engine light comes on temporarily to show it is working (along with the oil pressure and seat belt lights). Don't know if you've noticed but next time you start the car you might look-see if it comes on okay.

[Sfbradburn]

The check engine light does work on start up, and did cut on and off a few times yesterday and today.