constant rpm issue

danmf05 · Post by **danmf05** » Sat Jun 21, 2008 1:35 pm

Hey just wondering if anyone has had this prob and knows what causes it. I race my 89 beretta in a 4cly class and when racing the motor will cut out and drop 500-1000 rpms and then keep doing it, I thought it was low on gas but after filling it up it kept doing that. It idles fine, checked oil, new batt., any ideas out there. PLEASE HELP!!! THANKS.

SuzukiGhostRider · Post by **SuzukiGhostRider** » Sat Jun 21, 2008 8:13 pm

Run a fuel pressure test and let us know the results.

danmf05 · Post by **danmf05** » Sun Jun 22, 2008 3:49 pm

have not checked fuel pressure with guage but I know the pump is working good, and the filter is clear, with air filter off there is a constant flow of fuel, I can hold the pedal at a constant rpm and it will drop and work its way back up, the motor never dies its like it just losses power, Ill have to see if I can get a guage to check pressure unless anyone thinks its something else.

JeffD · Post by **JeffD** » Sun Jun 22, 2008 4:42 pm

yeah, just cause you can see gas at the TBI doesn't mean your getting the proper pressure, also check your ignition, both the primary and secondary components that means your coils, wires, spark plugs, crank sensor, wiring to the ignition modual and the modual itself.

danmf05 · Post by **danmf05** » Mon Jun 23, 2008 8:41 pm

the motor was just dropped in a month ago and at that time i check the coil packs and module, also put in new spark plugs and wires, I think I will try the fuel filter and let you all know, I have read a couple other questions on here and most have changed them with very little luck. But might as well give it a try.

danmf05 · Post by **danmf05** » Thu Jun 26, 2008 6:07 pm

so i replaced the fuel filter and thats not the issue, its the weirdest thing, just gasing it up and holding it at a constant rpm it keeps dropping and going back up. very fustrating.

SuzukiGhostRider · Post by **SuzukiGhostRider** » Fri Jun 27, 2008 8:31 am

That sounds like a miss to me my friend. Recheck your coil packs,plugs and wires. GL.

danmf05 · Post by **danmf05** » Mon Jul 14, 2008 5:44 pm

so after more tinkering we have found that the #3 cylinder is only running at about 60psi, where the rest are betweent 90-110, ran it at the track again last weekend and the hotter the car got the more it backfired, or atlease thats what it sounded like to everyone. anyone got any ideas...ive taken off the valve cover and the valves seem to be working fine....no dmg to top end of assy.

Money pit Beretta · Post by **Money pit Beretta** » Mon Jul 14, 2008 7:43 pm

Sounds like the valves are not closing fully or you have bad rings.

danmf05 · Post by **danmf05** » Mon Jul 21, 2008 3:21 pm

i think it might be the valves too, being the bad mech i am i messed up the rockers, i over tightened them, anyone know the proper way to tighten these so they dont open too far or not far enough.

Money pit Beretta · Post by **Money pit Beretta** » Mon Jul 21, 2008 8:10 pm

Did the valves ever hit the pistons? In the old days we would run the rockers down till the engine bogs down and then a back off of 1/4 turn. If the valves did get hit they are bent, best to put a new head on(guides will be trash also).

SuzukiGhostRider · Post by **SuzukiGhostRider** » Thu Jul 24, 2008 1:47 am

Best way I ever learned to tighten rockers was the old school way. Engine running , tighten until just snug (ie , no rocker play) then 1/4 turn tighter. Always worked like a charm for me. If you're sure you over tightened then probably the valve, but my money is on the rings. GL.

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