Question about 2000 Chevrolet Astro

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Engine surges especially at low speeds

Originally there was a code P0300. Also P1345 pending. I replaced a bad EGR gasket, cleaned some corrosion from EGR valve connector pins, and changed the spark plugs. Now I got a misfire code for #2 ... I'll check resistance on that wire tomorrow. The most noticeable problem is the surging at low rpms. It acts like the accelerator was being pedaled even when it's held still. Under load it works fine, although the surging is somewhat noticeable when cruising at highway speeds ... almost like driving into a gusty wind. I noticed the fuel trim numbers fluctuate a lot. Also the O2 sensor readings.

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  • allspice5 Dec 10, 2009

    saailer ... disconnecting MAF sensor didn't make noticeable difference. I checked it anyway and it looks clean. I just checked the recording of a slow acceleration and MAF readings seem to be relative to TP, Load and RPM, but I'm not sure of the time lapse between readings. Maybe it isn't possible to pick up fluctuations that occur 3 to 5 seconds apart.

  • allspice5 Dec 10, 2009

    saailer ... disconnecting MAF sensor didn't make noticeable difference. I checked it anyway and it looks clean. I just checked the recording of a slow acceleration and MAF readings seem to be relative to TP, Load and RPM, but I'm not sure of the time lapse between readings. Maybe it isn't possible to pick up fluctuations that occur 3 to 5 seconds apart.

  • allspice5 Dec 11, 2009

    saailer ... disconnecting MAF sensor didn't make noticeable difference. I checked it anyway and it looks clean. I just checked the recording of a slow acceleration and MAF readings seem to be relative to TP, Load and RPM, but I'm not sure of the time lapse between readings. Maybe it isn't possible to pick up fluctuations that occur 3 to 5 seconds apart.

  • allspice5 Dec 22, 2009

    saailer ... I cleaned the MAF sensor and problem reappeared in about 200km. I disconnected it and tried driving again ... it's not bad on hard or light acceleration, but it bucks and misses badly at even speed or light deceleration. I also occasionally get EGR circuit A low code. Looks like I'll need to change the valve, but I don't think it's actaully sticking ... moves very freely. Fuel consumption is similar to my 4WD pickup pulling a heavy load ... awful!



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Disconnect your MAF sensor and take the Astro for a ride. If you notice an improvement; Try cleaning the MAF with CRC MAF sensor cleaner.


I’m happy to help further over the phone at

Posted on Dec 10, 2009

Testimonial: "It does appear the MAF is the problem ... tried it again with everything warm and it works fine disconnected. Now I'm having trouble finding cleaner."

  • David Burbee
    David Burbee Dec 11, 2009

    Howdy! Disconnect the MAF sensor so you can enjoy the ride and head down to your local Radio Shack. Ask for catalog # 64-4338.
    It is a product called "Deox It/Progold; A twin pack of electronic device cleaner and contact cleaner. The cost is about $15. Spray the MAF with Deox It. Then hook it back up and test-drive.

    A replacement MAF will run around $130 at an auto parts store. This price includes a "core charge" of $30; Which means take back the defective part and the $30 is refunded.




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Related Questions:


EGR faults

1.6b) Symptoms of faulty EGR
Associated OBD2 error codes DTCs: P0400 - P0409; P1403 - P1409 other common codes can include 'multiple misfire P0300'

The EGR has two possible fault modes either it is 1) open when it should be closed or 2) closed when it should be open. (See also DPFE faults)

'Open' faults
  • Erratic idling: 'hunts' at idle with erratic engine performance when running. This is due to the air ingress through the split diaphragm or the EGR valve being left open, either event compromises the intake manifold vacuum and in turn this interferes with the ECU's ability to deliver accurate fuel to air ratio for a given engine speed.
  • Sudden engine stall: In addition to the rough idle, a hot running engine when quickly brought to idle (after the car comes to a halt at a junction) can stumble and then stall. The engine will hesitantly restart immediately: this is significant difference to Crank and Camsensor error.

'Closed' faults
  • Misfire and 'pinking': if the EGR is jammed closed or the exhaust feed pipe is blocked (with baked on carbon deposits) the engine runs lean and very hot, so hot in fact that the fuel air mix in the cylinder can spontaneously ignite causing a misfire. The misfire if pronounced can, in turn, be detected by the engine knock sensors (P0300) leading to a 'check engine light' warning and reduced engine speed limitations.
Inherently diesel engines create more soot in the exhaust and as a result blocked EGR assemblies are more common in diesels than petrol engines.
  • Burnt Exhaust Valves. Prolonged exposure to excessively high ignition temperatures brought about by a blocked EGR system can lead to exhaust valves being over heated to the extent that they become distorted and so no longer seat properly. Poorly seated valves prevent good compression.
  • Surging: A sticking EGR valve can lead to an effect of rhythmic surging a bit like the MAF fault, especially in turbo charged engines. Normally on a warmed up engine the vacuum from the inlet manifold opens the EGR. If the EGR fails to open promptly the turbo can be subject to a slight boost. Extra fuel/air mix is pushed into the inlet manifold as a result, increasing pressure (decreasing the vacuum). Without vacuum in the inlet manifold the EGR closes again but if sticky only does so slowly. This may allow inlet gases to flow through the EGR into the exhaust manifold for a split second. There is a time lag in the sequence of these events leading the engine to surge in cyclical manner.
NEXT 1.6c) EGR how to fix

on Jul 15, 2011 | Mercedes-Benz E-Class Cars & Trucks

1 Answer

What is code p0300?

P0300 - Random, Multiple Cylinder Misfire Detected Fault Code Definition
  • Random, Multiple Misfire Detected
  • Check Engine Light flashing
  • Rough running, hesitation, and/or jerking when accelerating
  • In some cases, there may be performance problems, such as dying at stop signs or rough idling, hesitation, misfires or lack of power (especially during acceleration), and a decrease in fuel economy
Common Problems That Trigger theP0300
  • Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
  • Incorrect ignition timing
  • Vacuum leak(s)
  • Low or weak fuel pressure
  • Improperly functioning EGR system
  • Defective Mass Air Flow Sensor
  • Defective Crankshaft and/or Camshaft Sensor
  • Defective Throttle Position Sensor
  • Mechanical engine problems (i.e.-low compression, leaking head gasket(s), or valve problems

Jul 25, 2014 | 2000 Dodge Durango

1 Answer

Slow acceleration, bogging down as if to stall, when I press down on the gas it soundsa like the engine reves up but no speed follows.

Most of the time, one defect triggers another, and so on, and if the primary problem is fixed, the other defects may clear when given some time.

The easiest of your Codes to fix is the P0401. This is an EGR airflow Code problem in the throat of the airhorn. The passageway which feeds the EGR is dirty. You need to clean the port between the intake and EGR.

Code 1131 is lean reading from O2. Can be restricted fuel injector or low pressure, or too much airflow to cylinders from a leak.

Code 1151 is a Vacuum leak. Can be detected with engine running by spraying water from a spray bottle to seams and lines.

Codes 1233, 1234. Bad connections on wire ends, (Known defect of Factory crimps) At fuelpump, inertia sensor, or fuelpump module.

You need fresh fuel. Fuel injector cleaner could help. The water spray can detect leaky gaskets that are dried up. You could easily have corrosion on connections, especially under the car.

Feb 24, 2014 | 1997 Mercury Grand Marquis

1 Answer

Increase then decrease idle when engine is cold especially

cold engine idle surge. (problem)
RPM range of surge not stated
300-700 or 800 to 1500? (range is critical to diagnosis)

bad fuel
running summer fuel in winter (running old fuel?)
needs a tune up bad, see the list in the operator guide.
idle speed controller,sticking or EGR valve same. (clean them)
location not stated, so cant guess about local air temps.?
no other symptoms, lack of engine power? etc?
was it ok last week, or better, when was the last time it was OK?
1week, 1year?
surge , causes, on a tuned engine might be:
1: too lean. so lean the ISC can not control idle. rpm low, stalling
2: too rich, flooding, stalling, spark plugs foul (look at them)
3: weak compression in 1 or more cylinders.
4: bad spark.
5: air leaks, in the plenum causing , ISC to lose control.
why high RPM?

well that means it fails hot too.
and there is a simple tests. for hot surge.
is engine fully hot? 180F and holds solid there?
say rpm is about 800
and you turn on head lights, heater fan and (not AC) and defrost.
the RPM must hold or the ISC is failing.
ISC -= idle speed controls. (all EFI has this function)

Oct 28, 2013 | 1996 Honda Prelude

1 Answer

1998 gmc z71 surges in drive p1345

The P1345 means SGC (Cam Position) sensor circuit malfunction/crankshaft position-camshaft position correlation
P0300 means random/multiple cylinder misfire detected

mpps ecu chips

Aug 07, 2012 | 1998 GMC Sierra

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DTC PO300 and PO506 engine won't idle when cold


Sep 04, 2009 | 2003 Pontiac Montana

1 Answer

P0300 Engine Code Ford ZX2 2002 ZTEC dual over head cam engine. Has 107K miles. Has new plugs, Only thing I really notice is when I turn on AC the car seems to stumble at steady speeds, especially...

P0300 Random Misfire

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

A Random Misfire code usually indicates a vacuum leak or bad gas.

NOTE: If a misfire in a specific cylinder should lead you to check the spark plug, fuel injector and compression.

Jul 25, 2009 | 2002 Ford ZX2

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