My 88 Targa seems to stumble more ofter than not when takinging off from a dead stop. The car seems to be idling a little rougher than usual and I'm not sure whether I 'm imagining it but there may be a slight loss of power. That may be my imagination because once I get over 3-3500 rpm the car accelerates great.
I recently changed the plugs to Bosh Platinums and saw a marked improvement immedialely, but 600 miles since then, things have gone downhill. I tried Techron thinking that might help but the stumbling is still present. I read mixed reviews on the Bosh plugs after installing them. Does this sound like its the culrprit or is it more likely a fuel delivery problem? Thanks for the feedback.

 

Hard to say Mike.....I'd get some good old Bosch copper plugs in there.

Fuel pressures would have to be measured, ....make sure your idle switch is working correctly, a nice cleaned/lubed ICV and AFM vane.......get some O2 measurements,....all, at minimum.

Then go from there..

BEST!

Doyle

 

I'd be more apt to look for a vacuum leak. Check the tq on your manifold connections, boots, etc. Some ether starting fluid aerosol work great for this. Spraying around the various connections will show an increase in idle speed at a leak.

Another way to do a rough check is to remove the oil cap while idling. You should get a noticeable drop in R's when you remove it.

I ran those plugs for 3 or 4 years with no problems.

 

I had a problem with Bosch Coppers and Platinums in my 88 Carrera (WR7DC), so I went with NGK BPR6ES. Problems with stumbling & hesitation went away. I would also check the CO reading to make sure it is in the correct range.

 

Just got back from a spirited drive after having sprayed ether starting fluid around hoses, seals etc (no leaks detected), checked oil filler cap (question follows) and added seafoam fi cleaner and filled my tank. I always use 93 octane which is easy to find in CT.
The rough idle went away completely but the stumble, while less, is still there but 75% better.
When I took the oil filler cap off there was an audible decrease in rpm but not enough to see watching the tach. I'm guessing in the range of 20-30 rpm. Should the decrease be a lot more?
Thanks everybody for the help. Mike

 

Well, it sounds like vacuum isn't the issue. Your description sounds right on the rev drop. Could be dirty injectors that are freeing up. Did the car sit for a while?

 

Took it out of storage in March and usually drive it 3-4 times a week. 20-50 miles per drive on average.

 

Injectors don't like to sit. That could be some of the problem. See what the Sea Foam does. Techron works really well, but should be timed to happen prior to an oil change.

Maybe next year, pull the injectors out a couple of weeks before recommissioning, and send them off to clean and test.

Did the car get stabilizer in the fuel over the winter?

 

Yes I put in stabilizer in a full tank of gas.

 

Well, that should keep the fuel from going to hell, but dormant injectors can still get sticky. When I built my motor, I sent mine off to be cleaned and they sat for about 2 months before finally getting put to use. 3 of them were DOA pending a little coaxing.

 

That's interesting. Thanks. I'll add it to the list of winter projects. I read about a company in Torrance CA that appeared to be very thorough. Is there a group you would recommend?

 

www.witchhunter.com!

Awesome company/service.

 

I've added it to my favorites file and will call them over the winter. Thanks!

 

I was able to tell which 3 cyls weren't firing @ idles by measuring exhaust manifold temps. They were basically cool compared to the others. Of course, this would also cause cold cyls if you had spark issues as well. I also rigged a 9V battery with two leads to open them as a check. With engine off, you'll hear clicking when energized. You could have 1 or 2 sluggish ones.

If you narrow it down, tapping on the suspect injectors with a screwdriver handle may help open free them up, if you have a rough idle, which I think you reported.

It's all process of elimination.