Good evening,
I am working on 1999 5.2l (this year has no EGR)
would anyone be willing to unbolt their TPS and put a shim in the throttle stop to set engine speed to about 1500, then while it is running, manually turn the TPS to see if it floods the engine? I did this test on mine expecting it to flood, but it made a little difference. Perhaps MAP is adjusting it.
My TPS passes volt tests, but the engine still coughs like it is running very lean. It starts at low throttle and up. Idle air control, MAP, temp sensor,charge air sensor, fuel pressure 35psi, flow all pass tests. Not sure on O2 yet.
I have read many posts like this on the search here and was wondering if anyone know if that was a way to test TPS?
Please let me know.
Thanks,
Scott

 

Isnt' fuel pressure supposed to be closer to 49 PSI? Low pressure would most certainly make it run lean. As would a failing O2 sensor.

 

Fuel pressure on the '94-95 was 39PSI. '96-01 was 49PSI. I'd guess the fuel pressure regulator is shot or pump is dying if the constant pressure is 35PSI on a '99, unless of course you recently replaced a fuel pump with an incorrect older model.

 

MAP sensor is the master controller for fuel injector pulse width. If the TPS signal is out of range, and the MAP is reading correctly, TPS data will merely be ignored by PCM and should trip a code.

 

Thanks for the reply.
I am glad you brought up fuel pressure vs year because the engine is 99 and the truck is 94. I see the later engine has different injector part numbers. It sounds like I have more work ahead of me.
Thanks,
Scott

 

What year is the PCM? The engine computer if your not hip to the lingo. If the puter is the 94 (I would assume yes to run trans) you just need the 94 injectors to bump up the duty cycle. I believe. Unfortunely, the only tuning option for the 94 PCM is a flash from B&G Chrysler.

I'm amazed you got the 94 PCM to work with the 99 engine sensors. Tell us more about what you did and didn't swap and we can maybe help a bit more.

 

If the PCM is the box on the pass side of firewall, I did not find a year lable on the pcm. The later engine was installed before we got it. My father inlaw got it as a first truck for my son and did not ask any questions. I first suspected an engine swap when I saw the temp sensor mounted in a plumbing tee in the heater ciruit. I had to pull the engine because the mount bolts were broke off in the block. Fix the flex plate to match the 94 tranny and I machined the intake to install the temp sensor where it belongs on the 94 by the thermostat. I have been trying to make the truck right since we got it.
I printed off pictures of all sensors to determine what year they are and found the throttle body sensors are 94. The injectors are 97 up and was wondering if you or anyone else knew if they 94 injectors would swap to the 99 manifold?
I found what looks like a 94-96 intake/egr/injector assembly for sale and was wondering if that would swap. I see the gaskets are different on the front and back of the manifold.

Please let me know if you are aware of the swapping questions.
Thanks,
Scott

 

The only difference of significance in newer Vs older intake manifolds is the EGR port in the back and a second bung for the two coolant sensors that the older trucks had. Though I've not had two in my hand to compare, I believe the older and newer fuel injectors are the same physical dimensions, just different flow rates.

 

I was looking on ebay to see comparisons and found several listings showing a manifold of the 94-97 being a type without EGR. Do you know if there was such a thing?
I got the impression that injectors may not swap from pictures of the different parts they had different shapes in the mount area. I suppose that does not mean they will not swap.
I started checking into a manifold assembly since perhaps not having an EGR as it should and the incorrect injectors sounded like the best approach if it will fit. I will test the o2 sensor first since I have not done that yet. It back fires through intake and cuts out under a load. I checked coil wires and cap today, the measure good. Checked timing last night. I am running out of things to check.
Thanks,
Scott

 

Just an update.
After correcting plug gap from .045 to .035, testing o2 sensor and rerouting plug wires, the truck runs much better without coughing. I have not driven one of these that is in top condition, so I do not know what to expect. To me, it is similar to my 82 Dodge 150. I rerouted the plug wires, because I found a Dodge service bulletin regarding cross fire. I will see how it goes for a while.
Thanks for the help.
Scott