It was suggested I put a thread in here in hopes of maybe someone seeing something I overlooked. The car STILL has the rough idle, the miss, the up down idle, the "Putting" sound from the exhaust as I call it. I have replaced a TON of stuff. Spent so much I could have bought a crate engine at this point.

In an attempt to rid the car of the "putting" or miss as it had at closed loop I have replaced the following and in some instances multiple's of them. Like the MAF, TPS, o2 and TB, I replaced several in case I got bad units.

MAF, TPS, throttle body, IAC, o2, fuel pump, fuel pump relay, coolant temp sensor, fan sensor, IAT, Bosch 3's, distributor, ignition module, cap, rotor, MSD ext coil, wires, plugs, removed manifolds installed headers, y-pipe, cat, full 3" exhaust, EGR, EGR Solenoid, every vacuum hose, thermostat, oil sender, knock sensor, air filters, timing chain, all gaskets on intake, plenum, runners, throttle body, timing etc replaced, pulled the push rods to check for bent re-set valves with engine running method, did a leak down and a compression check 175 across the board give or take 5, even pulled the injector wires and spark wires off one at a time to check each and there is noticeable difference with pulling spark off but not so much with injectors. Fuel pressure is in range, I've OHM'd the new injectors and there good, I've checked and rechecked the TPS and everything else I can check.

The ECM is new and all vacuum and wiring is intact and working. So in a nutshell I spent a small fortune on throwing things at this car to fix the putting/miss issue and it didn't fix anything. WHen I first got the car it had a really nasty rough idle along with the missing out. Changing out all that stuff made the car a tad better as far as the rough idle went. It did not, however get rid of the miss or "Putting" as It sounds coming out the exhaust and the vibration.

If anyone has any suggestions on what else it could be I would gladly listen. At this point I am about to unbolt the engine and slide a carbed 383 I have sitting in the garage down in her. I really want to keep it stock and keep the TPI but I can't keep fighting this thing. It obviously has an issue that's being overlooked. /sad

Thanks in advance.

 

Year,make ,model? any codes? you need to get it on a scanner. Look at the fuel trims

 

ugh, Frustrating, I just discovered loose lower intake bolts and bad intake gaskets on mine, solved my idle problem. You got good compression, vacuum readings?

 

I went thru that once.......ended up being a rounded cam lobe

 

87 Iroc 5.7... no codes, have had it on a scanner it checked out ok. That was the first thing I did when I bought it was take it to a shop. After 500.00 and a few days they said it was normal. Said fuel and spark was correct but it was a tad advanced. Also said it needed a tuneup and possibly injectors. They tuned it up before I had a chance to say not to but luckily I stopped in to see progress before they installed the injectors at 1500.00. So after leaving I ordered injectors and installed them myself and it still didn't do any good. That's when I started digging into other areas like the TB, relays, MAF etc.

I have a wideband as well and it shows normal while idle and at WOT it's logging 12.7 which that should be close to correct. Outside of the exhaust system, coil pack and Bosch's it's completely stock car. I was under the impression the Bosch were same as stock but better spray pattern so I couldn't see this messing with trims. However I am open to looking into something if need be, but I originally thought it was a rich condition at idle. Spark plugs show normal, exhaust ins't black or anything.

Under load I don't notice anything out of the ordinary. I can tell it's "chugging" while trying to hold steady speed but this could very well be the trans. It slips in and out of OD excessively and it shifts through the gears super fast, way to fast. The issue really(at this point) seems to be an idle/slow speed issue only. Off idle like mentioned above I don't notice anything but the steady speed issue.

 

Yes, as mentioned above compression is great and I checked vacuum today and it was great as well. Checked for leaks with propane and starting fluid. I don't have numbers with me there in garage but the motor popped out 175 on almost every cylinder. I know 1 or 2 cylinders were 170 and 1 was 179 but it was super close. None of the cylinders were far off or anything crazy.

I thought about the cam lobe being the issue or timing but I replaced the timing chain and as far as the cam goes I'm not sure. I have owned a couple cars that had bad cams and the cars would backfire, low power, popping, rough idle, low compression etc. I have none of those issues on this car. Off idle and under load the car has as much power as any other 87 TPI. I even thought about hole in piston or valves but I would think it would act up while in open loop or at WOT or under load for that matter no?

 

Is the TPS adjusted "corrected"?

 

Are there any other relays that could cause a sensor or MAF or something to act funky?

 

Gap the spark plugs correctly? I've forgotten that before, and it can cause a rough idle.

 

Could very well be injectors, was the issue oin several of my cars. A set of southbay injectors (the yellow ones with the little spacer ring) fixed it..made them silky smooth. Now, 1500 for injectors is just downright criminal!!

 

Slow speed, pay attention to proper IAC and TPS settings.

If everything else had indeed been checked, do you have worn guides?

Guide seals look ok?

Plugs oiled down whatsoever on suspected holes?

While not perfect, u can check lobe lift off the rocker with doing nothing other than taking the valve covers off. If one is out of whack compared to the others u have a place to investigate.

Hydraulic lifters can collapse as well and you don't get full valve actuation.

Cracked ring lands on pistons can do funny things as well as broken/butt'ed rings. Work fine when cold or vice versa when its hot.

I'm throwing things out there I've run across.

What a vacuum gauge do while issue is occurring.

 

As stated in my post, It's got a brand new set of Bosch 3's int it and I did pick them up from Southbay. Which BTW these guys are awesome. They answer emails even LATE at night if there is any issues. Made me a repeat customer for sure.

 

yes sir. Adjusted, re-adjusted, re-adjusted some more and even more after that LOL

 

I could partially agree with this causing some idle issues, but not what I described above. However to answer your question, yes, they are adjusted correctly. I've been through several sets and brands to rule out plugs as the issue. I wish it was a simple thing like spark plugs.

 

I have checked the heads and valves as much as I can with motor together. Even tossed in a snake camera and cylinders looked quite good actually. TPS and IAC are operational and set correctly.

Plugs are not oiled in any way. As stated when I pull them out they look brand new. If anything they look untouched like they were never fired. Which is what led me to believe originally that the issue was ignition or spark not firing causing inadequate burn which caused the rough idle. However I don't think this is the case as the entire ignition system is new. I also tested spark plug "spark" as a friend of mine brought over his snap on tester and it's putting out some serious voltage he said.

Rings could very well cause this issue but wouldn't compression be down if the rings were worn or broke? Compression was mid 170's on every cylinder so I ruled out valves and pistons a while back. However cranking an engine over is a big difference in actually running with combustion so I could see a ring causing this when it's running.

Vacuum was fine, it was like 21hg from the gauge with no major fluctuations at idle. I have tried to check the cam and lifters by scribing the rockers and checking height and it appears normal. No major slop or any single rocker out of whack. I set them by ear with engine running so it should be at zero lash with just a slight bit of pre-load which I turn mine 1/4 past tapping stop.

I thought about alot of this as well valve train and pistons but it doesn't add up that it does it ONLY when the engine goes into closed loop(when it's warm). That would make me thing o2, MAF, or some other sensor isn't working correctly. At first fire the car runs like a dream. After about 1 1/2 - 2 minutes when it heads into closed loop BAM rough idle, dying, etc city.

 

Something shorting out?

 

I would be suspecting MAF or ECm at this time, about all thats left, be nice if you had one you could swap out and test before buying it. O2 can be checked with a digital volt meter and test its output after warmed up and in closed loop

 

So I started tracing back wires to see if one is broke. Here is what I came up with. I believe the car has timing issues due to the ECM not controlling it properly. I went to set the timing but since the PO rewired a small portion near the heater core due to a previous fire, there is no water pack connector for the timing ECM wire. I see 2 tan wires, 1 is complete with no breaks and 1 is sitting, end cut, nothing on other end or no other tan wire for it to connect to. This could or could not be the timing wire.

So I am struggling to figure out what this wire goes to and where the timing wire is at. It's the ONLY wire under the hood that is not connected to something and it happens to be tan. I was under the impression from reading that the timing wire was Tan with a black stripe not straight tan? Either way, does anyone know if the timing wire that gets disconnected has any voltage going through it, or a way to trace to make sure it's the correct wire? Does anyone know the position on the ECM that this wire comes out of? It may be hooked up but I want to confirm it and then figure out what this cut tan wire is for.

 

http://www.austinthirdgen.org/index.php?pid=19 Find your wiring diagram on there, does show a tan/blk wire for timing . I see a tan only wire going to cold start injector.....

 

BAM.... so umm yea. When the PO spliced the harness back together from the fire, he hooked up 1 single wire wrong. Behind the motor is a hole with wires coming out. I assume this is for heater and AC controls. The PO hooked the timing wire from the ECM into this wire going back into the interior from behind the motor. So I simply unhooked it where he had spliced it and hooked the wire to the bare hanging tan wire that was unhooked.

The car is still vibrating so I didn't think it did any good however I took it for a 5 minute cruise and the car ran better. It had slightly more power when punching it and from a dig. It also doesn't die anymore when coming off speed to a stop. It idles pretty decent in the garage now as well. It still has a pretty bad vibration which mixed with the missing out it made it horrible at idle. Since I hooked the wire up right it still has rotating vibration but the miss seems to be gone now.

The brown wire controls just the advance no? I wouldn't have thought this would have made much difference in my problems since my issue was at idle in open loop and not while driving.

 

i would re-time the engine now.
sounds like this guy had a similar problem?
https://www.thirdgen.org/forums/tpi/...ing-issue.html

 

Yea I read his a while back when my car first had issues. His problem was a bad Dizzy from summit. My issue was from the start a mixture of things but mostly the throttle body leaking and the EST wire disconnected. I'm thinking the engine was timed wrong to begin with and with the EST disconnected it wasn't advancing like it's supposed to. I still don';t know why it would rough idle with the EST disconnected since it only controls advance. Of course if the ECM didn't get feedback at open loop it could probably cause other issues I guess.

It may not be fully fixed, it still vibrates pretty bad at idle and at different rev RPM's. Can anyone tell me what most of the wires coming out behing the Engine right where the distributor is? There is a small factory hole there and wires go through to engine from interior. Curious what those are as some of them are melted and cut flush there. I assumed they were for the AC/Heat since the PO installed an AC delete he didn't bother to hook any of that back up.

Also My Fan/FP? fuse keeps popping which makes sense why the PO rigged up a constant on fan system and bypassed the fan relay. I assume maybe one of those burned wires behind engine or else where is causing a short popping the fan/FP fuse. When I got the car the PO told me the guy he got it from rigged up the constant on fans cause the relay was to expensive for the fans. No I know the truth, it's cause he couldn't reach back and splice the wires on firewall due to engine sitting so close.