BlackBear

Hi,

I have an '87 that is stuttering at partial throttle. Full throttle is ok, no throttle is OK too. When I'm giving it partial throttle the motor starts to stutter or hiccup.

The car has Weltmeister chip. No idea is that is the source of the problem.

To eliminate it as a source I'll take it out first. Next thing are the spark plugs, wires, distributor.

Unless someone has a simple answer and I'm just way off track.

I'm open for suggestions.

Thank you.

Steve Weiner-Rennsport Systems

BB,

I think some attention to the basics are in order such as how long it been since the car received a thorough tuneup to establish a proper baseline. Cap, rotor, wires, plug connectors, plugs, fuel filter, air filter and in many cases, oxysensor are all replaced at this time.

Don't forget the DME relay, too.

After that, you can look at things such as the AFM's wiper, head temp sensor, etc.

ruflife

BB,

I've got the same problem on my 86 so if you find the answer please post it. My car doesn't follow any logical reason. Sometimes it is fine but yesterday it occured constantly. I retraced what I had done previously to no avail. Cap-rotor-wires-plugs all were original so didn't hurt to change them but the problem still exists. I am in the process of cleaning all my grounds . I had installed an optima and had to put in a new ground wire. Oddly, when my car does the miss as I call it, the radio has a split second cut out every 30 seconds or so . May or may not have anything to do with it but doesn't hurt to check. Next on the list will be 02 sensor,dme relay, reference sensors,cht sensor,......?

theiceman

ruflife sounds like you are having an electrical failure . i would be hooking up a voltmeter with a high sampling rate to your 12v line and see if it drops out when your radio failes or missfires. This is where one of those old fashioned meters is good coz you see the needle drop monentarily for your 12v.

RShepHorse

Has it been sitting around a while? If it's not electrical, consider injectors. Fuel Injector cleaner [Techron or Chevron Proguard] and a bit of an Italian Tune-Up did the trick for me this past spring for similar hesitation/stuttering.

ruflife

BB,

Changed out all these 25 year old parts - dme relay - both reference sensors and re gapped them to the flywheel - magnacore plug wires - plugs - cap and rotor - cht sensor - o2 sensor - and cleaned as many grounds as I could find . Miss is still intermittently present - stereo still does the same cut out. Next is a new ground strap at the transmission and an out of car injector cleaning. Earlier this spring I had to change out the alternator with a new ( not rebuilt ) unit . Wondering if it could be a possible cause if it is electrical and not mechanical/fuel related.

BlackBear

Thank you guys.

I have my radar detector set to display voltage. Not sure if the sampling rate is sufficiently high. It shows constant voltage above 12.

I'll try the injector cleaner and will inspect the ignition parts.

Thanks again.

ivangene

on the Carrera you have to set the idle solenoid (err what ever its called in the middle of your intake) the idle and the CO mixture all at the same time...the reason I know is I just had this problem and my shop just fixed it for me by turning screws and watching the readoout....

runs perfect again....they said the Carrera is not the same are SC or earlier in this respect due to the way the system woks....IDK... I couold hug them how good it runs, only cost me 45 minutes shop time!!

worth every cent!

Rick K

^^This. I had a similar issue to the OP- plus erratic idle. Smoke test revealed no vacuum leaks. So I replaced all the basic tune-up items above + the head temp sensor and new fuel pump. It didn't do the trick, problems worsened over time. I cleaned original ICV, then had to replace with new - erratic idle went away, but still idled rough and had some "dead spots" on light throttle. Replaced the AFM with a refub'd unit and now all is well...

It may not be one thing. Start with the basics and work from there...good luck.

BlackBear

Thank you.

Is AFM air fuel meter?

dshepp806

Assuming all the completed work was sufficiently completed, with no bad parts, I'd definately get a voltmeter meter on her to see what that new alt (and, hopefully new regulator) is doing.....

Doyle

ron mcatee

AFM = Air Flow Meter

dshepp806

Aside (maybe?), sometime during the first year of ownership (of my 89)---and having read numerous threads here and there re: the AFM,..I removed the cover on it and gave her a check, at least as far as the wiper contact condition....having worked in electronics, the tests were quite simple,..making use of one of my trusty analog meters,..put the scope on it, also. I was able to clean up the trace areas (slight burnishing) and did not see any noticeable wear at the suspect idle point on the sweep...SO;;;didn't touch anything-adjustment-wise, jsut made sure the trace and contact arm was VERY clean.

More preventative than remedial, really...however,..a bad spot on that AFM would cause issues (I would think),...but moreso, repeatedly (not intermittently)....especially at part throttle......

radio blanking is a real big clue.

Best!

Doyle

Rick K

If that ends up being the issue, just as an FYI, I sourced the refurb'd AFM from Parts Heaven (510-782-0354) in NoCal for cost + core charge. I talked to Al there who was a super helpful guy...

rusnak

The afm diagnostic test. No need to open it up to test. You need a 9v battery: http://www.the944.com/afm.htm