Hi,

my 87 TA 305 tpi is misfiring badly...used to miss only when it had been running for a few hours (not depending on water temp), and only a couple seconds at a time. Now it runs rough from Idle to 5000 rpm No matter how long its been running. I've tried to fix it with the following:

New Pick-up coil, new ignition module, new cap+rotor, new ignition coil, new wires, new plugs, new fuel filter, tested the fuel pressure (37psi @idle) and injectors (all at 16.7ohms), and cleaned the air filter.

It misses in both open and closed loop. I tried running in "limp home mode" by unplugging the MAF, TPS, and O2 (seperately) and it still misfired all 3 times.

Any help/tips are very much appreciated...starting to run out of hope (and cash)...
thanks, nick

 

The ohm reading on the injectors does not tell the whole story. You'll need to get them checked out for flow. That is, make sure they're all flowing per factory specs. One or more of them may be clogged with dirt.

Also get a so-called "noid" light from Pep Boys (or equivalent). With the engine running, pull off one injector plug at a time and plug the noid light into the connector on the harness. The light should be flashing in sync with the engine.


Also, if the injectors are ok, then it's time to run a compression test on the cylinders. If any of the cylinders seem suspicious (low pressure relative to the others) run a leak down test on it. If it fails the leak down test, either you have bad cylinder heads or bad rings. Do you notice any blue smoke coming out of the exhaust?\

 

it puffs out blue smoke when first started, but cleans up quickly. Every once in a while there is a small puff of smoke while it is idling.
I picked up a compression gauge today but haven't had a chance to use it yet. Should be a good time pulling the plugs out from under the headers again (just put a new set in yesterday...took 2 and a half hours ).
thanks for the reply, nick

 

Blue smoke on startup can indicate bad valve seals, I would get those checked out. You could be getting oil in the combustion chamber, in turn fouling out one or more of the plugs. How did the old plugs look when you pulled them? If they are oil soaked, you need to address the problem. How did it run with the new plugs? still missing?

I would also recommend running some injector cleaner. Can't hurt to start cheap.

 

I had bosch platinum plus 4s in there (for about 3,000 miles). I heard that they foul quickly in our cars so I took them out. One plug was completely fouled, and 3 more were on their way. The rest were ok. When I put the new plugs in (ac delco rapidfires gapped at .035) it still misfired. I also tested the wires while I was changing them out and they came out fine. Tried about 5 bottles of injecter cleaner, no improvement at all. If its cheap, I've tried it . After i drink some coffee im going to go out and use my compression guage. I'll let you guys know what i get.

Nick

 

You should have hired your Father to come out and help you fix that broken injector harness wire.