Hey folks,

I have TBI engine that has been giving me grief for the longest time.
During the summer when temperatures are high, it runs pretty good even when cold - but only if you just start it and get going. If you let it sit an idle, even for just a very short time - it starts running real rough and pouring out black smoke.

Now when the cold weather is coming - it just keeps getting worse. It runs poor even if I get on it right away.

When saying it runs poor - I mean poor acceleration, black smoke, rough idle, no power etc.
This all appearantly clears up as soon as it reaches normal operating temperature.
However, I have noticed that over the last few months I've gotten severly lower mpg's.

The problem has been there since I got the car about 2 years ago, but has gotten worse lately. When I got it, it was bone stock. The last two winters I've been running a block heater to make it run a little smoother at startup and make it reach operating temperature faster and thus minimize the problem.

This is whats done to it at this point:
Full exhaust and headers
Catco hi-flow cat
K&N filter
New plug wires
New Cap/Rotor
New sparkplugs
New Temp sensor
New O2 sensor

Im at a loss and would very much appreciate any pointers to help me straigthen this out before winter really kicks in here in icey cold Norway!

Thanks!!


Ken

 

Ok this might sound stupid but that happend to my TBI besides the black smoke...it would run fine in summer then in winter it would run like crap till warmed up...like it would idle rough would have no ***** and sometimes even stall when first starting it up in winter till it warmed up.....and believe it or not...it was my damn fuel filter..dont ask my why it acted up soo bad in winter...maybe cuz of how much metal contracts in winter...but when i changed that it fixed my problem right up...so if u havent done that the 8 bucks is worth it to see if it will work

 

Have you tried changing the O2 sensor? It sounds like something is happening in whichever loop the ecm is in when it's below normal operating temp. You understand what I'm saying right? (cuz it's easy to get lost when i try to explain something i'm thinking)

 

Thanks guys!

Red25thRS,
I have not replaced the fuel filter, so I'll give that a try and see what happens. Either way Im sure it wouldn't be a bad idea to replace it ..LOL

BadBlue91RS,
I forgot to add the O2 sensor to the list above of things that I have replaced, but I infact did that last week.
I totally understand what you are saying, and the O2 sensor was one of my best bets as well..but no such luck..

If there are other ideas besides the fuel filter - keep them coming!

Thanks again


Ken

 

Try replacing the IAT.
Which temp sensor did you replace? There are 3 coolant temp sensors, 1 for the gauge, 1 for the fan, and 1 for the ecm.
I'm betting it's either the IAT or the MAP sensor is flaking out. If it runs rich on cold startups then I'm thinking IAT.
Which spark plugs are you using? I'd go ahead and double check that the gaps are all still correct. If you drop a spark plug 98% chance it'll land right on the electrode creating a nearly grouned spark plug.
I doubt it's ignition, definatly sounds ecm related.
Does the SES light work (come on with key on but turn off with engine running)?

 

Hey JPrevost,
I replaced the CTS for the ECM.
On the IAT, are there any tech articles on replacing it? I havent worked much on the TBI, mostly on the TPI so some info on the replacement would be awesome!

At the time Im using Accel plugs that I just installed a week or so ago along with the headers. I regapped them all before putting them in. I've had at least 4 sets of plugs in it (Autolite and NGK's before the Accels) and they have all been regapped before install but the car has been running poorly with all of them. So Im pretty confident that the plugs are not the problem.

Yes, SES light works on startup, but has never come on otherwise.

Thanks man!


Ken

 

The IAT is in the air cleaner. It's the only electrical sensor there. Just pinch the side prongs with some needle nose pliers and pull it out. New one just pushs in.
The only other thing I can think of is a leak ahead of the o2 sensor. That would cause it to report lean and dump in extra fuel. Set your base timing to 6 degrees and see if you still have the problem. I thought the code would report a bad IAT sensor but it might not.
If I were you I'd get some kind of datalogger hooked up. Winaldl or Diacom. This will tell you if all of the sensors are in spec. There is an exception.... I had a bad CTS sensor that was flaking out at a specific frequency. So fast that winaldl never could see it. I found it using my lockers setup (fast data capture) but I'd never have found it if I hadn't had my tcc locking and unlocking.

 

black smoke --> too rich.
.
Any chance you could swap out the fuel injectors
with two known good ones, for a test?

 

What wiring harness branch does the IAT lead come out of? I ask, because I'm the third owner of a vehicle, and simple don't have the IAT in the air cleaner

 

Look around the rear of the engine on the passenger side. it may have fallen down and is resting along the firewall or back of the engine. The IAT harness is fairly long and can get lost in the compartment if it is not secured to the firewal or air cleaner assembly.

 

That only thing I've been able to find is a "Mystery Lead" coming out of the ac compressor harness branch..... I wasn't sure if that was my bad boy or not. PS - it's an 88 - I'm not sure if they changed the harness around in the later years