I was wondering if you guys could help...? Here's what I'd posted:
Ok, my always-helpful board reps, here's the problem, with the symptoms....after the car sits for overnight, maybe a little longer, when it's started the next day, the idle is HORRIBLE - fires up, climbs to 1200, spikes down to 600, back up to 900, drops back down to 500....it's all over the board. Once the car's been out driving for about, 5-10 steady minutes, though, the idle returns to it's normal 600-700 that it always used to run at. However, though it does run smoother, I swear I can feel the fuel cutting for a split second every now and then - like, if I accelerate on WOT, it'll speed up...then maybe the revs'll drop just a little bit halfway up the tach. It's hard to explain, basically it sounds like I'm not getting all the fuel I need all the time. So, what do you guys think..? Simple plug/wires, maybe fuel filter, or fuel pump....? What else could the problem be...? It happened once a few weeks ago, after sitting a night...but after driving it for a week straight after that, the problem never returned, until recently. I'm hoping it's something I can handle myself, as I'm doing my best to subscrible to the theory of "paying a shop = evil when you can do it yourself"....any help would be MUCH appreciated....'87 2.8 MPFI, if it matters. (Injectors..? Hmm......)

 

fuel pump relay f*king w/ya? maybe a loose ground somewhere? check all electrical connectors, use DVM on continuity & start moving the wires around.

 

I had exactly the same, changed MAF, ICA, EGR nothing.
Finally it was the ECM

 

check you wires first. occasionally i would have a rough idle, and during acceleration it would feel like a cylinder wasn't fireing. it would feel real jerky and the rpms would move all over. make sure none of you boots are cracked. for me it ended up ended up being the middle boot on the passenger side was cracked and the spark was arcking out to the alternator brackets. check it out it gets REAL hot in there. make sure none of the boots are cracked. pop the hood at night and start the car. you will be able to see any sparks that may be jumping. (i found that out after i did my fuel filter, O2 sensor, distributor, and ignition module). it was the easiest thing.

i would say if you haven't done you fuel filter. do it anyway. its cheap and easy. buy a fuel pressure gauage (40.00) it will let you know if its your fuel system before you spend too much money. and you will use it forever!!

check to see if your car is throwing any codes. that'll help too!!

 

I get that problem, and I even have it now. With school & work, I don' t have a free day to fix it. But my "fix" has always just been tuneup-related... I'll either have a bad wire, fouled plug, wrong timing, etc. I totally agree 100% with SAEspinz80 about the fuel pressure gauge. (And I've changed the pump twice on my car already.. )

You can nab a cheap digital voltmeter/multimeter from www.harborfreight.com, or if you want a SunPro one on closeout, check out SunPro's website, in their garage sale section: http://www.sunpro.com/cgi-bin/web_st...e.htm&cart_id= Click on the "Test & Tune", then choose the first meter. I'd buy the Sunpro over the Harbor Freight ones. The HF ones don't specify that they have a 10 meg ohm input, and the SunPro one does. That 10mOhm input is important for not killing your computer/fuel injectors when doing certain tests. I have both (HF one first, then the Sunpro).

And I'm STILL jealous of WaynesRS because HE got an original "as packaged in the store" BOX! My Sunpro meter came in a ziplock bag. ('Course the bag was inside a regular shipping box, but STILL! Damn!)

 

to give up credit TomP, the fuel pressure guage idea came from you when I was having all my issues. More than worth the 40.00

 

By all means do a full tune-up. Not too expensive, and can't hurt having all new stuff in there. If you haven't I would definately change that fuel filter. Before I changed mine, I'd have to give it some gas on cold start ups. No more.

 

I think I've used that FP gauge at least 10 times since I've got it. The one thing I -hate- is that a TBI motor doesn't have a port for a pressure gauge! They sell an $80 pressure gauge that comes with a hose and the port on it- you remove the TBI feed hose, and put this "special" hose in it's place, then hook up the FP gauge. The gauge itself is the exact same as we have, for port fuel injection. The only difference in that price is that stupid hose. One of these days, I'll go pick up a junkyard TBI's fuel feed hose, splice it, and put a t-fitting on it that will meet with our gauge's valve.

But as far as port injection, I've used it on my car many times, and at least 3 or 4 times on relatives/friends cars.

Hm.. I guess it could also be a misadjusted TPS, dirty IAC valve/passageway, bad CTS (coolant temp sensor), or, like you thought, bad/clogged injectors. (Do the injectors last, I doubt they're the problem, since the car runs fine when it warms up. Besides, one that's very leaky would show up on the fuel pressure gauge.)

 

Hey, a lot of excellent suggestions, guys, it's quite appreciated....since the warm weather seems to finally be here, I'd already purchased my tune-up stuff and will get to it probably tonight. The only reason I'm not REAL sure about wtf was going on is stuff like this: this morning, went out, started up the car....got the now usual spikey RPM's, 1000, then 400, then 600....it rode rough on the way to school, gradually getting better until I got there. 5 hours later, I go out, start up the car, and drive out...no problems! I figure this doesn't really sound like a pump problem, because that would be a constant....fuel filter seems to be the most logical (and cost-effective) solution...I'll keep my fingers crossed and change it tomorrow...any more thoughts are still welcome, and I'll let you guys know how it goes. Might as well change the plugs and wires while I'm at it....damn 6th plug, way the hell in no-hand's land...

 

Definitely do your tune up, but when you encounter a "hunting idle" that generally indicates a vacuum leak. Probably a small one like a cracked hose.

The reason you are especially noticing this when "cold" is the engine is not in Closed Loop yet, you are in Open Loop. Hence, the ECM must run off tables. Once warm, you are in Closed Loop and the ECM is using the O2 sensor to compensate.

But if the "tune up" doesn't fix it, look for a cracked hose causing a vacuum leak.

 

I have that same problem, whenever I first start up the car. I am beginning to think it's the ECM. The guy who sold me the car gave me all the records on the car and way back in some records a shop thought the ECM was bad but the service was never done. I know a Chevy dealer told me it needed a tune up, but that is pretty broad. I'd like to know how you fix it Azure.

 

small world, I still am having trouble when driving and my car studders but quickly smooths out.

but I had the wacky idle too, and it was the vacuum hoses that goto the fuel canaster. the hoses were so dry rotten in that area from the heater blower to the block. that the hose was being sucked shut because it was so weak.

 

Don't know if this will help, but when you said SPRING time - I'm thinking MOISTURE. I heard this story one time about this guy that would wash his car & put it in the garage & shut the doors - next morning his car wouldn't start. The moisture from the car wash condensed under the hood - caused all kinds of electrical problems. Once he drove the car, it was fine - He could find no problem. I think they put him in a mental institution some place.

They make a clear Spray stuff that is supposed to seal your wires n' stuff - but it's a temporary fix.

 

Once again, I'm going through everything, checkin' it out..just thought I'd say I will tell everyone when I'm all fixed. thx.

 

Hey Tom,

Do you use a gauge on TBI cars alot??? In my personal experience, checking FP on a TBI car is RARELY useful. Here's why:
1) You can check for fuel presence by lifting the air cleaner.
2) They don't hold rest pressure.
3)They only run at about 10-12 psi so you'll usually have a no-run condition with a weak pump. No-run's are easy to diagnose.

BTW, at work we use a custom(home-made) fuel line with a schrader valve tapped in it. We splice it in between the fuel filter and the fuel line......but, i've only used it probably twice on a TBI car.

 

Actually I haven't used it once on a TBI car. My sister's old car was a TBI FWD 2.5, and wouldn't run one day. Tried everything; but couldn't check fuel pressure. Turned out later to stump my mechanic, who swapped everything out for "spare parts" (all sensors, injector, computer, TBI unit, etc), and got it to run, but he couldn't say how. He undercharged us a lot because he felt like he didn't really solve the problem. He even replaced the fuel pump, with no change.

So TBI doesn't hold pressure when the engine's not running?