engine hesitation
Thread Starter
Cruising
Joined: Aug 2013
Posts: 12
Likes: 0
From: Branchville SC
engine hesitation
I have a 1990 vette that has the L98 TPI engine I've already changed apark plugs wires and checked distributor cap and rotor, Checked fuel pressure(41.8psi) qnd changed the map sensor. The engine hesitates when throttle is opened up and sometimes pops a little is there anything that may come to mind that will help solve this problem' The engine has 74,000 miles on it. Also the INFL REST light is on, Ihave already cleaned and applied dielectric grease to sensors. Its not showing any faults right now on scanner. Help JDBUSTER !st vette
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The "pops a little" symptom is a timing problem 99.99% of the time. Your timing might be too far advanced. Check and set to 6° BTDC. Disconnecting the EST connector will set error code 42, so be aware that will happen. You can ignore it and the ECM will purge the error after 50 restarts.
When I had a hesitation it turned out to be a vacuum leak. They can be very subtle and not in an obvious place. Mine was where the PCV hose connects to the intake manifold. Another non-obvious one is an EGR valve that is not closing completely.
When I had a hesitation it turned out to be a vacuum leak. They can be very subtle and not in an obvious place. Mine was where the PCV hose connects to the intake manifold. Another non-obvious one is an EGR valve that is not closing completely.
Thread Starter
Cruising
Joined: Aug 2013
Posts: 12
Likes: 0
From: Branchville SC
I checked for vaccum leaks but found none also checked EGR valve using test method shown in forum. I tested the TPI it loses voltage about midway throttle opening then jumps back on with 3.0 ma. by tester. going change this frist and see if it helps. If not will still need help Thanks if you think of anything esle please lett me know
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 413
From: WV
I checked for vaccum leaks but found none also checked EGR valve using test method shown in forum. I tested the TPI it loses voltage about midway throttle opening then jumps back on with 3.0 ma. by tester. going change this frist and see if it helps. If not will still need help Thanks if you think of anything esle please lett me know
Pro
Joined: Aug 2010
Posts: 617
Likes: 17
From: Hamilton Ontario
Thread Starter
Cruising
Joined: Aug 2013
Posts: 12
Likes: 0
From: Branchville SC
I changed the TPS and it made a world of differance, engine runs great. Now to tackle the INFL REST light. I cleaned the sensors on Frame and added a ground strape to top side of sensors and installed new bolts on frame so I have a good ground. I read something about a K pin is that located on the analizer plug for car and what position is it. I think it said to ground to seat frame for three seconds with key switch in on position.
