Kyle Karbum

Almost there. Only missed one thing on the third test, HC ppm by 7. So close.

Anyways the timing was set at 28 degrees BTDC when I bought it. Got it set at the correct 10 degrees and it seems like it ran smoother at 28. Smog tech said he thought it was misfiring. It does seem sluggish / missing at lower rpms. And when turning hard left it almost dies. I'm guessing it needs something in the fuel pump/tank area.

Could it be a weak fuel pump?

Not really sure what else to check. Already replaced ignition coil, spark plug wires, and spark plugs. Distributor looks fine.

Kyle Karbum

Additional Info: 1986 Jeep Cherokee 2.8L v6

1st test was right when I bought it, no repairs.

2nd test was after a month of working on it, couple hundred dollars worth of new parts.

3rd test, only difference from 2nd test was correct ignition timing and a can of Seafoam.

dac612

My suggestions:
1. do a thorough fuel pressure check.
2. do a thorough vac leak check
3. do a thorough compression test.

You could potentially slap a fresh cat on it to get done with the test then figure it out after. You are pretty close after all.

Post up your numbers on 1 and 2 and hopefully we can help if you didn't already figure it by then

Kyle Karbum

Yeah the smog place said it would definitely pass with a new cat, but I figure with it being so close I can pass without one. Sure seems like a costly fix for only 7 ppm.

Have already checked the vac lines. Replaced a bunch. Pretty sure every thing is correct.

I'll do the fuel pressure test and post up what I find. But for the time being, seems like a few quick fixes might get it to pass and then I can deal with the misfire later. Not sure which of these would help to knock off just a little HC, any suggestions?

1 - Set the timing to 8 degrees instead of 10. Pretty sure they have a tolerance of +/- 2.

2 - The muffler is 30 years old and needs to be replaced. I know it doesn't directly contribute to emissions, but could it make a difference just getting a new, clean muffler on there?

3 - Heard a bit of E85 can lower HC. Not sure if I want to try this one but anyone else know if it works?

4 - Another can of Seafoam for good luck.

Any other ideas to knock off a bit of HC?

dac612

Try isolating the missfire by unplugging 1 injector at a time to figure out which cylinder is missing. (if no change in behavior when you pull an injector plug, that cylinder probably isn't firing)

Maybe you have a dead or partially plugged injector causing a lean condition and therefor high hc reading. I mean you're definitely close. But the misfire can still be related so I'd troubleshoot that

Kyle Karbum

Well got the compression test done. Cylinder#4 does seem a bit low but hopefully close enough that it doesn't mean anything major. Got numbers, anyone know what they mean?

First number is dry, second number is wet.

Passenger side
cyl1 - 150 - 165
cyl3 - 150 - 160
cyl5 - 150 - 165

Driver side
cyl2 - 145 - 160
cyl4 - 135 - 150
cyl6 - 150 - 160

Kyle Karbum

Additional Info:

1 - When I did the compression test, spark plug gaps were a bit big, knocked em down to the correct gap and it's running a bit better. Pretty sure I'll pass smog but still want to get it running in top shape.

2 - When really gassing it, high rpms (~4000), and I quickly let off the accel for a fast shift, it backfires sometimes. If I move the timing forward it backfires less. At 28deg it doesn't backfire at all. 10deg is standard.

3 - Has smoke out the exhaust on cold startup for a few seconds. Read it could be valve seals.

4 - Has a small oil leak. Not exactly sure how much as I have only had the car a few months, but seems about 1/2 quart every 3000 mile oil change, maybe a little bit more.

Oswalla

Not a fix, but a bottle of Heat before test should get you past at 7ppm over.

Kyle Karbum

Heet in the yellow bottle or Iso-Heet in the red bottle?

Also should I run it through and then take the test with clean fuel? Or should I take the smog test with Heet still in the tank?

mrfacundo01

I have a 1991 that failed smog really bad.
HC PPM CO PPM NOX
15 MPH 86 MAX MEASURED 255 0.73 MAX MEASURED 4.97 711 MAX MEASURED 623
25 MPH 103MAX MEASURED 246 0.93 MAX MEASURED 2.23 613 MAX MEASURED 670


I have no clue where to start. What parts did you change and how did you go about diagnosing the problems? Many thanks in advance.

I guess this is why people register there cars in other states that they don't drive often.