Hard start and won't rev past 3500

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bluekon

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So just bought a 99 Tahoe 4x4 5.7 all stock other then a magnaflow exhaust... Truck was in rough shape when I bought it by currently I have one lingering problem I can't get rid of... After sitting for a bit it will just crank and crank but not fire... Fuel pump is coming on and sounds like a healthy pump... So it cranks and won't start cycle the key to off and start again it fires right up but first crank it will crank for 10 min and nothing. Now once it is started runs and drives great idles perfect etc but if u stomp on it it almost hits a rev limiter at 3500. Crusing around thought its absolutely perfect. Also only does it under load in neutral it revs fine
To make things worse it has one CEL code p0355 crank position sensor fault.. So I thought that makes sence replaced the crank sensor cleared the code and same problem came back with the same code...

Anyone have any suggestions on were to even begin thanks in advance!

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JenneK

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It could be the wiring or the plug going to the sensor. Have you inspected all the wiring and tested for breaks?
 
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bluekon

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No haven't done that yet and I wrote so
Something wrong the chek engine list isn't on but the code is still stored
 

purple 'hoe

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A google search and I got nothing for that code. I will look it up on GM Service Indicator tomorrow morning and report back to you.
 

ch4d

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What does that mean?

The COP (coil on plug) ignition system is what is used on most modern engines. There is an individual coil for each cylinder that is controlled by the PCM (powertrain control module). It eliminates the need for spark plug wires by putting the coil right above the sparkplug. Two wires are dedicated to each coil. One is a battery feed usually from the power distribution center. The other wire is the coil driver circuit from the PCM. The PCM grounds/ungrounds this circuit to activate or deactivate the coil. The coil driver circuit is monitored by the PCM for faults

If an open or a short is detected in the driver circuit for coil #5, a P0355 may set. Also, depending on the vehicle, the PCM may also shut down the fuel injector to the cylinder also.

Symptoms

Symptoms of a P0355 DTC may include:

MIL (Malfunction indicator lamp) illumination
Engine misfire may be present or intermittent
Causes

Potential causes of a P0355 code include:

Short to voltage or ground on COP driver circuit
Open on COP driver circuit
Loose connection at coil or broken connector locks
Bad Coil (COP)
Faulty Powertrain Control Module
Possible Solutions

Is the engine misfiring presently? If not, the problem is likely intermittent. Try wiggle testing the wiring at the #5 coil and along the wiring harness to the PCM. If manipulating the wiring causes the misfire to surface, repair the wiring problem. Check for poor connection at the coil connector. Verify the harness isn't misrouted or chafing on anything. Repair as necessary

If the engine is misfiring presently, stop the engine and disconnect the #5 coil wiring connector. Then start the engine and check for a driver signal to the #5 coil. Using a scope will give you a visual pattern to observe, but since most people don't have access to one there's an easier way. Use a Voltmeter in AC Hertz scale and see if there's a Hz reading of between 5 and 20 or so that indicates the driver is working. If there is a Hertz signal, then replace the #5 ignition coil. It's likely bad. If you don't detect any frequency signal from the PCM on the ignition coil driver circuit indicating the PCM is grounding/ungrounding the circuit (or there is no visible pattern on the scope if you have one) then leave the coil disconnected and check for DC voltage on the driver circuit at the ignition coil connector. If there is any significant voltage on that wire then there is a short to voltage somewhere. Find the short and repair it.

If there is no voltage on the driver circuit, then turn the ignition off. Disconnect the PCM connector and check the continuity of the driver between the PCM and the coil. If there is no continuity repair the open or short to ground in the circuit. If continuity is present, then check for resistance between ground and the ignition coil connector. There should be infinite resistance. If there isn't, repair the short to ground in the coil driver circuit

NOTE: If the ignition coil driver signal wire is not open or shorted to voltage or ground and there is no trigger signal to the coil then suspect a faulty PCM coil driver. Also keep in mind that if the PCM driver is at fault, there may be a wiring problem that caused the PCM failure. It's a good idea to do the above check after PCM replacement to verify there won't be a repeat failure. If you find that the engine isn't misfiring, the coil is being triggered properly but P0355 is continually being reset, there is the possibility that the PCM coil monitoring system may be faulty.
 
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bluekon

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Sorry p0335... Checking fuel pressure tomorrow im guessing it's a weak pump
 

ch4d

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What does that mean?

The crankshaft position sensor (CKP) measures crankshaft location and relays this information to the PCM (Powertrain Control Module). Depending on the vehicle, the PCM uses this crankshaft position information to time the spark properly or on some systems it is only for misfire detection and does not control spark timing. The CKP sensor is stationary and works in harmony with a reluctor ring (or toothed ring) that is attached to the crankshaft. As this reluctor ring passes in front of the CKP sensor, the magnetic field created by the CKP sensor is interrupted and this creates a square wave voltage signal that the PCM interprets as crankshaft position. If the PCM detects that there are no crankshaft pulses or if it sees a problem with the pulses on the output circuit, P0335 will set.

Symptoms

NOTE: If the crank sensor is used only for misfire detection and NOT spark timing (this varies with the vehicle), the vehicle should start and run with MIL (Malfunction indicator lamp) illumination. Also, some vehicles require several key cycles to illuminate the MIL. If this is the case, there may be no MIL illumination until the problem often enough over time. If the crank sensor is used for BOTH misfire detection and spark timing, the vehicle may or may not start. Symptoms may include:

Vehicle may not start (see above)
Vehicle may run rough or misfire
MIL illumination
Causes

A P0335 "check engine light" code could be caused by:

Damaged CKP sensor connector
Damaged reluctor ring (missing teeth or not turning due to sheared-off keyway)
Sensor output open
Sensor output shorted to ground
Sensor output shorted to voltage
Failed crank sensor
Broken timing belt
Failed PCM
Possible Solutions

Using a scan tool, check if, when engine is running or cranking, that there is an RPM signal.
If there is no RPM reading, then visually inspect the crank sensor and connector for any damage and repair as necessary. If there is no visible damage, and you have access to a scope, you could check the CKP 5 Volt square wave pattern. If you do not, then, obtain a resistance reading of your crank sensor from a repair manual. (There are so many different types of crank sensors that there's no way to put here which resistance reading is correct). Then check the resistance of the CKP sensor by disconnecting the sensor and measuring resistance of the sensor. (It is best to check resistance readings from the PCM connector. This rules out any wiring problems from the start. But it does require some mechanical skill and shouldn't be performed if you\'re not familiar with automobile electrical systems). Is the sensor within resistance specs?
If not, replace the CKP sensor. If so, recheck resistance reading from the PCM connector. Is the reading still okay?
If not, repair open or short in the wiring to the crank sensor and re-check. If the reading is okay, the problem is intermittent or the PCM may be at fault. Try reconnecting and checking for RPM signal again. If there is now an RPM signal, wiggle test the wiring harness to try and induce the fault.
This code is basically identical to P0385. This code P0335 refers to Crankshaft Posistion Sensor "A", whereas P0385 refers to Crankshaft Position Sensor "B". Other crank sensor codes include P0016, P0017, P0018, P0019, P0335, P0336, P0337, P0338, P0339, P0385, P0386, P0387, P0388, and P0389.
 

JenneK

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No haven't done that yet and I wrote so
Really? It doesn't say that anywhere in your post.

If you have a code that points to a bad crank position sensor and you've replaced it with a known good sensor, you need to inspect the parts (wires, plug) that send the sensor's signal to the PCM.

However, I think you're on to something with the fuel pump. Since it starts after you turn the ignition to ON for a second time, it tells me that it is repriming the fuel system. Since it is a hard/no start condition after sitting, sounds like the pump is leaking down.
 
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bluekon

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Well when I replaced the sensor I visually glanced at the connector and wiring didn't see anything noticeable... Still haven't had time to chek pressure hopefully today
 
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bluekon

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Initial turning the key to on fuel pressure 35 psi
Cranking while trying to start about. 55 psi
And running at idle @60psi
 
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bluekon

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Yea I thought like 55 do that explains the hard star unfortunately couldn't drive it with the gauge in it to see what it did at 3500
 
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bluekon

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Replaced air and fuel filters today no change in either problem took the intake tube off to get a better look at things... Opened the throttle body butterfly to find this not sure if it's normal or not
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BattelWagun

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Yeah all that carbon is normal unfortunately. You can thank US emissions standards for that... As for the 3500 rpm issue; yes, the pre ignition fuel pressure seems quite low IIRC. Even though it idles fine and runs properly at a round 60 psi at idle, the pump may not be able to keep up with the fuel consumption rate at higher rpm's, and starts to lose pressure, causing the engine to sort of "hit a wall". You could try to replace the pump and sending unit to see if it fixes the issue, but I would try to get that code sorted out first.
 
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bluekon

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The code is off replaced the crank sensor and no code for about 100 miles... I'm gonna have to put the fuel gauge back on it and try it out again
 

BattelWagun

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The code is off replaced the crank sensor and no code for about 100 miles... I'm gonna have to put the fuel gauge back on it and try it out again

Alrighty then, well that helps narrow things down a little. So you're saying in park/neutral it'll rev normally to any rpm, all the way up to redline. And in gear it struggles to get past 3500?
 

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