Author Topic: 87 Chevy Runs then dies  (Read 354 times)

Offline dc7432

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87 Chevy Runs then dies
« on: June 02, 2023, 10:05:44 AM »
87 Chevy V20 w/ TBI 350. Truck sat for a few months went to start ran for a minute than died. Air cleaner was 100% packed with a mouse house. Clean out and would start for a few minutes then stalled. I installed a fuel pump relay and can hear both pumps in the tanks prime. Same results. Installed an ignition coil and control module. Same result. I had all the parts so I didnít have to buy anything. This morning (cold) started like normal and is currently running. Iím waiting to see if anything happens when hot. A few years ago I had the same issue and it was the distributor so that was replaced. Any ideas on whatís going on and yes there is gas in both tanks. Thanks!

Offline dc7432

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Re: 87 Chevy Runs then dies
« Reply #1 on: June 02, 2023, 10:07:52 AM »
Forgot to add installed a new in-line fuel filter.

Online bd

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Re: 87 Chevy Runs then dies
« Reply #2 on: June 02, 2023, 12:01:10 PM »
Any trouble codes stored?  Safely rig up a fuel pressure gauge and monitor the pressure to see whether it is constant at 11-12 PSI with the engine running and whether the pressure drops just as the symptoms occur.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline dc7432

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Re: 87 Chevy Runs then dies
« Reply #3 on: June 02, 2023, 12:04:47 PM »
Engine was hot fine at idle brought the RPMs up in park and it started to load up. Check engine light went on. Got code 33 (MAP sensor) and code 44 (lean exhaust). Not sure what to do next.

Online bd

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Re: 87 Chevy Runs then dies
« Reply #4 on: June 02, 2023, 01:25:47 PM »
Make sure there are no vacuum leaks in the vacuum line to the MAP sensor.  Spray around the base of the throttle body using some aerosol carburetor cleaner to verify there are no vacuum leaks.  Then follow the MAP Code 33 diagnostic procedure, attached.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline JohnnyPopper

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Re: 87 Chevy Runs then dies
« Reply #5 on: June 02, 2023, 02:21:01 PM »
bd is the MAP affected only at idle?

Was running my R30 55 mph on the freeway and got 13, 33, 44.

New O2 sensor. MAP is not.

Note: old gasoline.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Online bd

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Re: 87 Chevy Runs then dies
« Reply #6 on: June 02, 2023, 02:42:30 PM »
As an oversimplification, think of MAP as equivalent to the power circuit in a carburetor.  The ECM interprets engine load using the MAP signal to monitor intake manifold vacuum.  If a MAP goes out of calibration it will cause the engine to run all wonky.

ALWAYS diagnose trouble codes beginning with the lowest number and working your way methodically UP the list!  Your issue may be due to a poorly grounded O2 sensor or an open in the sensor lead to the ECM.  It could also be a faulty sensor.  Try connecting a temporary ground to the base of the sensor, clear the codes and re-road check.  Avoid removing and reinstalling an O2 sensor repeatedly or you may discover that it seizes in the threads.  Use nickel anti-seize on the threads if necessary and torque the sensor to spec.  You may also need to ohm out the sensor lead running to the ECM and/or clean and re-tension the terminals connecting the harness to the ECM.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline JohnnyPopper

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Re: 87 Chevy Runs then dies
« Reply #7 on: June 03, 2023, 03:07:55 PM »
All good advice, will perform and add results.

Thanks bd!
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline dc7432

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Re: 87 Chevy Runs then dies
« Reply #8 on: June 04, 2023, 07:30:52 AM »
Replaced the MAP sensor. Cleared the codes and running like normal. Thanks everyone.