Stock 88 2.8. Ok, it has been developing an issue over the summer. An intermittent whole engine cut out with accompanied tach drop. recently dropped out long enough the tech1 could have caught an rpm reading, but it wasnt hooked up at that moment. I backed up yesterday, and it quit. in mydriveway. Finally!!!! now i can diag easily. And i dont even need a tow truck. great day. But... i was not at all expecting to see the rpm read 3,000 rpm(ish) at key on, and then see it go up 160rpm while cranking. VERY puzzled with that one. I think i am smelling a bunch of raw fuel too. i believe it may be fueling for 3,000 rpm! I already have a spare distributor, ign module (which i keep in the car at all times of course), tach filter (i got to speak with THE Rodney Dickman!), and pickup coil. Probly could have solved the issue by just throwing parts at it, but i like to know.
So,,, anybody else see 3,xxx rpm while cranking a no start?
[This message has been edited by ricreatr (edited 09-28-2024).]
Probably a severe vacuum leak. Check the EGR tube for cracks. If the engine sounds as though it has a normal idle and the tach reads high check and replace the tach filter.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
[This message has been edited by Dennis LaGrua (edited 09-28-2024).]
So if I get what you're saying, it reads 3000 rpm high, no matter what rpm it's at? (0 engine rpm 3000 tach rpm, 160 Erpm, 3160 Trpm?)
Is it "fueling" even when the engine is not rotating (key on engine off, tach 3000 rpm, is the fuel pump running, and do you hear the clatter of the injectors, all that going on would be very obvious without the normal engine sound to drown them out.)
When it is flooded, having your foot to the floor while cranking will tell the ECM to turn off fuel, allowing it to clear the flood, and hopefully start, don't know whether doing that will impact the smell of fuel or not.
well, i cant figure a vac leak causing a false rpm reading on the scanner. The tach reads normally. the scanner (tech1) reads about 3,000rpm key on engine off. and another 160rpm faster when cranking. i did try clear flood mode with no fire, but was not surprised - when is this thing actually firing the spark plugs if it thinks the engine is spinning 3,000 rpm? i did not tear into it this weekend, maybe tomorrow.
If the tach and scanner both read 3000 RPM even when cranking, its probably a bad tach filter ( that little silver can with a wire lead next to the distributor) or the VSS on the transmission or a wire to it is shorted..
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
