tiger4life

Hi guys. I'm new here and trying to get some info to help my dad. Trying to diagnose the truck's problem before he decides he wants a new truck he can't afford

He bought the truck about 2 years ago with a small miss. Recently tried to get the miss fixed and his guy messed up a series of things that lead to him getting someone else to put a used replacement motor in. I'm good with cars but just not familiar with his, so I'm looking for info so I can get this fixed.

He has a 99 Chevy 1500 with a 305. The miss is now worse. It misses when idling and through the rpm band. Misses when cold and when hot. Looks like it isn't burning all of the fuel. The tail pipe is sooted and you can smell it. It had a misfire code last time I checked and the check engine light is on again after I cleared it.

I just want to know what I should check. The plugs, wires, distributor, and fuel filter are new. He used the spider off of the new motor so I guessing two bad spiders in a row would be bad luck, but who knows.

I'm thing of checking:
1. the fuel pressure
2. the maf (is there a procedure for this?)

Any advice would be appreciated...........

hicksvilleshick

check fuel pressure, check what kind of spark your getting. I had an ignition module (located under distributor) giving me fits somewhat similar to what your describing.

tiger4life

Ordered my fuel pressure gauge today.

tiger4life

Made some progress today. I found two problems.

1. Fuel pressure gauge came in today and I found that the pressure is not within the 60-66 psi range. It's 55 at idle and 60 at wot. Fuel filter is new, so does that mean I'll need to replace the pump soon?

2. My uncle and I found the big problem. No spark at the wire end for cylinder #4. The wires, distributor,etc... are new. Is there any other thing to look at except the computer? The guy who sold him the motor is saying he can have the computer, so we'll go pull it out of the tahoe tomorrow. Can we use the tahoe computer in a 1500 truck?

HOMESLICERYRY

Check Engine grounds as well, mine acted VERY similar

MDTAHOE

If it has no spark at the end of only 1 wire then your problem is either the distributor cap or the plug wire. NEW DOES NOT MEAN GOOD. Swap the wire with another cylinder if it follows the wire replace them if not replace the dis. cap. Since your truck does not have individual coils the computer has no control over your issue. GM truck computers almost never fail.

tiger4life

Thanks I will check this tomorrow. Today my father also decided to tell me that the Tahoe motor is a 5.7 instead of 5.0 like his original. He still has his original ecm. Could that be causing a problem?

tiger4life

Don't really know what to do with the truck next. Thursday, we grabbed the tahoe computer and the truck would not start with it. I read that it would do that because of different vin numbers, but didn't listen.

We put the original computer back in and it was able to start. So I checked the cylinder #4 wire again. It's deciding to spark now.

If it doesn't rain tomorrow, I will check distributor cap tomorrow for damage.

The 55 psi pressure is concerning me, but I don't want to throw $200 at a pump unless I know it's causing the problem.

Any other advice would be appreciated greatly.

tiger4life

Replaced the rotor and wires today. The rotor contacts were corroded and we got a replacement under warranty. It was only 2 months old. I changed the wires since I tore the boot on one of them.

Started it and got happy since it didn't miss for the 1st second or two. Then it started missing again, although it seems that it isn't as bad as before. I really think it's the fuel pump. I think after the initial rush of fuel, it's bogging down because of the pump's inability to keep up.