Yesterday I replaced the intake manifold gaskets - both lower and upper as well as the gasket around the fuel injector and the one on the throttle-body. Everything went on without a hitch and everything is dry though we now have a shifting issue. I will list the full process we did for better clarity.

2000 Chevy Blazer LT 4.3 2WD

Issue one - had fuel leaking from a fuel line under distributor cap. Removed cap and threaded it on snug after cleaning grit off. Fuel line stopped leaking. Considered fixed.

Issue two - No tachometer. Found the electrical plug that goes to distributor cap and plugged it in. After disconnecting the battery for a few minutes. Light went away and tachometer came back.

Issue three - Accidentally broke off plastic connector to vacume line under air intake near throttle body. Super glued it back on and we hear no vacuum leaks.

All lines are connected, electrical is good, etc. Its all dry and we changed the oil as a "kitchen sink" method to ensure nothing got in the oil galleys or down in the valley of the engine. We even took a shop vac to it to make absolutely sure nothing fell in during intake manifold install.

Distributor went in the same exact position it was in and cap and rotor had no issues going back on at all. All marks made lined up and the picture we took before removal looked the same. Mark on firewall was also in line with landmark from picture. All seemed good.

Engine runs very well. No shakes, and power off the line.

The issue we have now is that it shifts like a dog. Almost like a double shift. Or rather, it doesn't know when to shift. Rpm goes up and then a bump bump and now it's in second. Same for all other shifts moving through the gears.

Does anyone have any idea what could be causing this? No other parts than the intake gasket was changed out. Any help would be greatly appreciated.

 

The sensor inside the distributor is the camshaft position sensor. It has absolutely no effect on the tachometer, or engine performance, whether it's plugged in or not. Data from the sensor is used by the PCM, along with crankshaft position sensor data, to detect and accurately identify cylinder misfire. When the distributor is reinstalled, camshaft retard must be checked and adjusted. The adjustment aligns the sensor with the camshaft, and also assures that the rotor is aligned with the terminals inside the cap when the ignition coil fires. The adjustment is done by slightly rotating the distributor. Data is viewed on a capable scan tool, spec is zero degrees, plus or minus 2 degrees. If the adjustment is off more than ~27 degrees, (distributor gear not meshed correctly with the camshaft gear) the check engine light will come on and P1345 will be set in memory. If the check engine light is not on, and there is no P1345 in memory, the distributor is meshed correctly. If the adjustment is between 0 degrees and ~26 degrees, the check engine light will not come on, but there will be crossfire inside the cap causing engine misfires. The misfires may or may not be detected due to camshaft retard being out of spec. These misfires could easily cause problems with transmission performance.

EDIT: At 90K miles, it's due for plug wires, and AC Delco distributor cap, rotor, and spark plugs.

 

To clarify, when I connected the electrical connector back to the side of the distributor (not the cap, i mis-typed) then everything worked onward regarding the tachometer. I'm sure you are correct though this causes some confusion on my end.

I'm getting the codes pulled later today though and that will point me in a sufficient direction though. Just for turds-and-giggles, would that possible cause the shifting issue?

 

Just thought I should clarify some more info.

Distributor cap and rotor replaced 3 years ago
Distributor replaced 3 years ago
Fuel filter replaced 2 years ago
tune up done 2 years ago
Heater core replaced 3 years ago
spark plugs replaced 2 years ago
TPS replaced 2 years ago
coolant sensor replaced 3 months ago
throttle-body cleaned 2 years ago
MAF sensor cleaned 2-3 years ago
alternator replaced 2 years ago
shocks replaced 2-3 years ago
Fuel pump replaced 2 years ago
O2 sensor behind cat replaced 1-2 years ago
catalytic converter replaced 4 months ago
Climate control module on dash replaced 2-3 years ago
Compressor and Orifice Tube replaced 2-3 years ago
Shift kit installed 3 years ago with new fluid and filter

Updated signature to reflect updated mileage. We are currently at 143,000 miles now.

 

If the distributor is moved, removed, replaced, or the hold down bolt is loosened, camshaft retard needs to be checked and adjusted. The odds of getting camshaft retard within spec, without using the scan tool, are stacked well against you If camshaft retard is not within spec, crossfire inside the cap will ocurr, guaranteed.

As for the parts you've replaced: These things are very fussy when it comes to the fuel pump, distributor cap, rotor, and spark plugs, they really need to be AC Delco, (Delphi). Aftermarket stuff doesn't last, and in some cases, doesn't work when it's brand new. Might want to check fuel pressure and leakdown. Low fuel pressure and/or excessive leakdown can cause shift problems too.

Post the DTC's in the order they are retrieved.

 

Thanks! Will update once I get a scan tool on it.

 

Couldn't get to a scan tool yesterday. What we did do is recheck everything just to make sure. We decided to put the engine at top dead center. Notches lined up on crank shaft, aligned rotor with mark on distributor housing and put it all back together. Runs good still. After connecting the battery, it shifted great!

Then about 10 minutes of it running and we headed to turn some rental tools back in, it started to shift bad again but now only on the 1-2 and a bit of a shudder during acceleration. I still plan on getting codes pulled but maybe this new bit of info could help.

Other things to not is I had to put a bit of pressure on the line going into MAP sensor to pull distributor bolt out with a wrench. Checked transmission fluid. A bit dark but still red. Still no leaks from intake manifold repair. I can't say enough how well this engine runs at idle parked. It's only when it's been on for a few minutes that it starts to shudder and lurch at 1-2 shift now. Before that, I had full power and no shifting problems. We also tested the TPS and showed .7 with a smooth rid up to 4.7 volts though I had no extra hands to have someone tap it while we tested it.

Thanks. I'll continue to update.

 

The business about driving 10 minutes and then acting up is interesting. If you can get your hands on a scan tool overnight, there are some tests that can be done with the engine stone cold. The tests are done after the vehicle has been off for 10-12 hours, BEFORE you start it.

 

Replaced distributor cap, plugs, wires and rotor. Runs great and the funny 1-2 shift is now less prolific but more random. On my way to work this morning, it did it 3 times out of 7 accelerations off the line.

Did a leak down test and all is good. That rules out fuel and ignition. Got a random misfire code pulled yesterday but no code now with a friends scan tool later than night after the ignition tune-up.

I'm stumped.

I'm currently working on procuring a scan tool for an overnight test. Could you elaborate on what you intend?

 

Update. Drove it to work this morning and rode it during lunch. Problem has lessened on the second go around. Could this be a tuning issue within the PCM that requires some drive cycles?

If it isn't better by end of day today I will take a quick look at the 1-2 accumulator while I have the transmission pan down for an oil change just to rule that out.

Still waiting trying to procure a scan tool.