countzero

I hate to post without doing a 'full' search first...I took a quick look and I think some thread may apply but I'm not sure, and I'm very tight on time.

What happened was that the car had been running great until one day a few weeks ago it started dying when it dropped to idle speed. I had just filled the gas tank about 20 miles before so I first suspected a bad tank of gas. Therefore I drained the entire tank as best I could and put some fresh gas from another station in. (The 'bad' gas doesn't look quite right, kinda yellow instead of gold and it smells funny, but seems to burn ok in the lawn mower...).

After this the car still wasn't running well and was getting loud and smokey. [edit to add: excess smoke from exhaust, not off the engine]. I shook the muffler and it had crap rattling around in it so I swapped a newer muffler onto it from another 'parts' car. The thought being that maybe the shot muffler wasn't supplying proper backpressure. I also am wondering if my cat is shot.

Looking into it further, when I pulled the air filter, there was a lot of smoke coming in through the inlet just under it, before the air enters the MAF. I found that if I pulled one of the vacuum lines above the MAF and plugged it, this stopped but the car still runs crappy. It does seem to run ok at higher RPM's though misfiring? a bit. It just dies at idle though.

So, my suspects or "parts of interest" include this list: MAF, O2 sensor, CHTS, cat, and maybe the PCV. The fuel filter is fairly new, as are the dist cap and wires, and plugs. I've never messed with the ECU and codes but could check this out if worthwhile.

Wondering what any of your thoughts would be on this...I'm leaning toward a bad MAF because it is all black and sooty, but I don't want to burn out another one if there's some other cause for this. I do have a 'known good' MAF in a parts car I could swap in, as well as just about anything else.

Thanks - I have about a week to mess with this before I'll be forced to limp it to the shop and let them have at it. I am going away for a week then, and need this car back on the road.

vernk

is the smoke black or blue?

countzero

I think it's pretty much all black, but I've been working up front and just noticed an unusual (and strange smelling) cloud of smoke that's coming from the tailpipe. If I stick something under the throttle cam to keep it running, that still holds true, but I only did that once or twice and usually didn't think about it until I was giving up for the day and shutting down.

Another way to think about it:

1. What are the symptoms of a burnt out cat? It seems that I read you can't tell without actually analyzing the smoke or taking the cat out and having it tested. Doesn't entirely make sense but let's say it's true...but if the cat was bad could that alone cause a car to run badly like this?

2. Assuming that it has nothing to do with the cat, which other component would most likely cause this? What I know about the MAF is that *usually* the symptoms are very rough running and it won't go over 2000 RPM. Right on the first count but not the second - this baby still revs up past 2000 just fine. It just won't idle.

3. If it's the CHTS, from what I've read it causes the engine to run rich after warming up because the ECU can't tell that's warmed up. That might be a fit, except that it runs just about the same whether cold or hot.

4. Might the O2 sensor be more likely? I've had these go bad on other vehicles in the past but don't remember specifics. I don't remember it being this bad though.

5. Maybe it's a combination of the above (or something else). But why more than one component would fail simultaneously is beyond me, unless it was a chain reaction or one was already bad but not noticably until the second went bad.

It irritates me that I haven't been able to find the problem, although I haven't had a whole lot of time to mess with it and my right arm is in a cast from knuckles to shoulder which makes it hard to do some things (to put it mildly). Again, I have several parts cars, one '87 that got hit in the rear and bent the frame but was running well. I could pull just about anything from that one to swap in but I hate to pull the thing apart unnecessarily...I may end up swapping that whole engine into another car. Two others I have are an '85 and an '86 - not sure if everything is the same in those and neither has been running since I got them (I suspect that both have a slipped timing belt - saving those for another day).

Alex_V

A bad cat smells like rotten eggs and kills your top end power. Even though the VG doesn't have any.

~Alex

vernk

well if you have black smoke it means that your running rich i would take the car or you might just be able to take the vin into a dealer before you start switching to many parts i had a 87 that was running really rich like that so i took it to the dealer to have them put it on the computer and come to find out that there was a recall on the injectors and sub harness.

benalcoa

definately

maximase86

iTrader: (24)

The VG does have a CAT and a pre-cat. Mine did. Definately a bad O2, bad chts. I would start with those 2 and work your way from there. Also have you checked to see if you ECU is throwing some codes? That might be a better starting place.

madgun68

I'd start with the basics and work from there.

Pull the codes from the ECU. Is it showing anything?

The o2 sensor can sort of be checked using a multimeter if you have one. Just check for resistance between the two wires. If you're seeing it, leave it unplugged and start the car. You should notice a difference in the way it runs right away.

PCV valves are cheap. Not reason not to replace one if you aren't sure when it was last changed.

Just for measure, double check that all the plug wires are seated on the plugs. This sounds dumb, but with all the crap in the way, it can be difficult to tell. (I had this problem when I was working on mine.)

Check all the hoses to make sure nothing is cracked or came loose if you haven't already.

countzero

Yeah, I'm familiar with the injector problems and recall....I should check this out either way but had no problems before. Isn't this injector problem something that goes on continuously, or could it come on suddenly like this?

countzero

Have done a fairly complete check of vacuum hoses and such...found a few that were hard/cracked/rotten at the ends so I cut off the bad parts. Probably should replace them all.

Did a quick check of the plug wires and they seem ok, next I would have liked to put on a spark tester or pull them one at a time (if I can keep the engine running).

The O2 sensor check seems like a quick and easy way to rule that out.

I guess I need to bite the bullet and become friendly with my ECU. The Chilton manual seems to have a very convoluted troubleshooting guide for reading ECU codes - does anyone have a "cheat sheet" or quick checklist? Seems like I saw something on this board a while back.

Thanks all.

max95q

iTrader: (10)

What they all said, lol. Checking ECU codes would help alot.

vernk

i'm not sure if it would start suddenly but i would say its worth a shot, my 87 was flooding it self out like that when i got it and i didn't know why so i just took it in and was going to drop the $70 to have them look at it and walked away with a new set of injectors free.

countzero

I was able to try a few things today after work, before my arm started hurting like hell (recent surgery) and it started getting dark (no garage).

First, I went to check the O2 Sensor, and noticed that it was already unplugged. Hmmmm, I don't remember doing that....plugged it back in but no difference in the way the engine ran. I realize that the sensor is bypassed when cold (open loop) but no difference when warm either.

I did a visual check on the MAF screen - it is very black and after shutting off the engine, the wires did not glow or get hot (not even warm). So I'm thinking this guy is my primary suspect, but I'm not ruling out some of the other components yet. I hope to have time tomorrow or Thursday to swap the MAF with a known good one. Maybe I should get a new O2 sensor while I'm at it. If nothing else, if I can at least pull the good MAF from the other car and send it along to the shop, they won't have to go find me a new/used one at several hundred dollars - been there, done that.

madgun68

Pretty common for cars that are aging.

I just bought a set of NGKs and find it hard as you-know-what to get them in.

Having a multimeter is pretty good for doing quick and dirty checks. Not always accurate, but better than nothing. (Got one for $3 not too long ago.)

Getting it to the right mode is pretty easy. You just pull out the ECU so you can reach the turn screw on the side (should be a sticker next to it.) Once you can reach it, turn on the ignition and then turn that screw all the way. Watch the two l.e.d.s next to it. They'll blink.

Once it's blinked three times, turn the screw back. This should put it in diagnostic mode. Once there, it'll start flashing the errors on those two lights. (I think first is red, but maybe green.) Anyway, the first one is the tens, second light is the single digits. Each set represents a number. (Like 22 or something like that.) Then match those to the corresponding numbers in the manual.

To clear it, just disconnect the battery for a minute or two. Next time you start the car, the computer will re-train itself about the engine.

Good luck!

Yayomax

How long ago did you get your injectors serviced? I tried alot of things but the injectors. That was going to be my next step

vernk

I had that done like 5 or 6 years ago that car went to the junk yard like 3 years ago, input shaft barings went and couldn't get a tranny cheep enough and the body was getting bad from being a MN car in hind sight i should have kept the engine and such but not having my own place and moving around makes that kinda hard.

I think the ones in my 85 are leaking cuz when I first start it in the morning it acts flooded till I rev it up a bit then its fine. I think the ones in my 89 max and 90 pathfinder will work.

countzero

before you hijack my thread (just kidding), I thought I'd post an update.

Just got the cast off my arm today so I'm a bit more able to do things, although the arm is weak and it hurts like hell after using it just a little. Anyway, when I got home I pulled the MAF out of my daughter's old '87 that has a bent frame and is being scavenged - it was running well previously and had its MAF replaced a few years ago. If I'm up to it, I'll put that in the '88 tomorrow and see what happens. Then either way it's going in the shop while I'm out of town next week - I'll let them go over it and make sure everything else is ok.

One question though...the MAF on the old '87 has all 6 connectors, and also has an extra ground wire added that runs over to the engine. The '88 however only has 5 connectors present in the six pin plug. This is consistent with the wiring diagrams: 1987 non-digital has 4 ECU conns, one to interlock relay and one to ground, while the 1988 non-digital has only 3 ECU conns, plus the same other 2. The missing ECU connection on the 1988 is to pin 30.

Should I just snip leave it this way or is there actually a difference in the MAF units? The plug is the same and will fit. Wondering if that extra ground connection is an important 'field modification'. I know I've read some posts here about adding ground connections to some components (because the factory ones are not reliable?) and wonder if this falls into that category.

Thanks - Dave

vernk

sorry don't mean to hijack your thread random thoughts that get typed, anyway don't know if this will help you or not but this is from my 85 FSM

countzero

That looks like the diagram for the '87. The '88 though does not show the pin 30 connection to ECU from MAF. Not sure why.

Anyway, I put the 'known good' MAF in, and the car seems to run significantly better but still not great. I'm leaving for the airport soon so I'll be dropping it off at the shop to see what they come up with. In addition to all this, the car is just approaching 100K miles and I don't have a history on the timing belt so I'm thinking I should have that done - there are some noises coming from that area and I don't want to lose a pulley or throw the belt.

I guess I'll post an update when this is resolved. Thanks for all the help.

Next project - getting my '86 running, stay tuned.

-Dave

madgun68

Do post what is found out about the car. I'm interested to hear what it winds up being.

The computers in these cars seem to track just enough to keep the engine running well, but sometimes not enough to track problems.

My '88 was would run fine for a bit and then would random switch between running lean and normal. When lean, it would stumble and the rpms would bob up and down. I checked all the hoses and didn't see any obvious problems. I listened to the fuel pump (which I could barely hear) and it sounded like it was not running smoothly. Switched it out and it was fine. At no time did the ECU ever throw a code.

countzero

It was the throttle position sensor. I was able to pull a good one from my daughter's old car, so I don't know how much it would have cost me. Shop only charged me about $50 to diagnose and install it. Car runs great now.

Oh yeah, I guess the MAF could have been shot also, since I did swap that out. Guess I'll never know unless I try using the old one again. As much as those cost I won't be throwing it out unless I test it first.

Sorry it took me a long time to reply - been very busy, now that my cast is off and I can use my arm again...

vernk

good to hear you got it all fixed and your cast off

countzero

Well, I do wish it was running even a little better. Seems a little 'off' at times - could be timing or injectors. Plus, oddly when holding the accelerator steady the engine seems to vary in power slightly (oscillate is the word that comes to mind...), and my daughter's '87 does this too. Anyone else had that? [Edit: just answered my own question when I saw another thread on this topic...sounds like it might be the timing belt]

I need to do the timing belt before too long on my '88, it just hit 92,000 miles. But I really don't have much time to mess with it right now. I need to do some body and frame work on my silver '87 that's been up on blocks for a year. That one has more miles but is like new inside, unfortunately it's rotted out around the left rear wheel well and the fuel fill door. I can work on that for 'free' (my labor and scavenged parts only) but the other stuff would take some $$ I don't have right now, and more time than I want to have the '88 off the road - I need it to get to work 50 miles away. I've also got this '86 sitting here that may only need some minor work to get it running. I'll probably start another thread when I find the time to get into that one.

Thanks again for all the suggestions here.

madgun68

I get that surging too, but only when the car is cold.. After that, it runs just fine.

Actually, my black Maxima has started to act like that, but I'm only planning on driving it another week before it just becomes a backup/project.