Maristar 225 LT1 starts and idles but won’t rev

[maristar225]

I need some help. I have a 94 maristar 225 VRS that starts right up and idles perfect. But when you throttle it it dies almost immediately. Out of gear you can get some rpms if you rev it very slowly but put it in gear and dies just barley above lidle.

So far I have

Changed both fuel filters and cleaned the tank

Changed the IAC valve
Changed the map sensor
Changed the TPS

The fuel psi at the rail is 38 at idle and when it dies and with the fuel psi regulator unhooked it’s 43 psi wind still dies.

[Shaun R]

Check and make sure you are firing on all cylinders and didn't break a wire or lose a coil pack. LT1 will idle smooth with two missing cylinders then start having issues once under load. Crank position sensor is where I would look next if not an ignition issue.

[maristar225]

Thanks I’ll check all that first thing in the morning

[Shaun R]

There is a thread in the engine section of the forum specifically related to the crank trigger sensors. And those ignition coils are from a Caddy Northstar motor and easy to source.

[maristar225]

Ok thanks

I broke down and bought a scan tool but just realized the diagnostic port is an odd ball. Do you know what kind of adapter i need to read the codes?

[Shaun R]

I believe they were the old jumper wire and count the blinks but I could be wrong. Mine never threw a code so that’s something I never looked into.

[2kcustom]

I’m having the EXACT same problems on my maristar 280 with an 8.1. Please let me know if you find out what the problem is!!

[bret]

I think is still correct for pin out and LED bulb for code reading...maybe others can verify before you try, I had this saved in a file on my laptop. If you bought an OBD code reader it won't fit, MEFI connector:
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1) Ignition key “OFF”

2) Remove the cap from the Data Link Connector (DLC)

3) Slide the LED into the female terminals of position E and F on the DLC, making sure that the positive side goes into terminal F and the negative side into terminal E. No damage will occur if you get it backwards, it just won't work.

4) Turn the ignition key to the “ON” position. The LED should come on steady.

5) Insert the half paperclip into terminals A and B – This puts the engine in “Service Mode” and codes will begin to flash on the LED. On 1996 and earlier engines you may hear the fuel pump come on. If not you should be able to hear the Idle Air Control (IAC) motor move. Use care in this step, do not insert in the wrong terminals or ECM damage could result! Look closely, the terminals are clearly marked.

6) Read codes by observing LED flashs. If the self diagnostic system is working it will flash code 12 – one flash, pause, two flashes, long pause – it will repeat three times. If other codes are present they will flash in order of lowest to highest. Continue to read codes until the code 12 sequence is repeated.

You can also be clear codes (by moving the throttle to 100% and back) and set base timing while in Service Mode.
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[maristar225]

I just got a MEFI cable and software and plugged into it today it doesn’t seem to show anything wrong. Unless I am missing something all the values seem to be changing as I would expect on all the sensors

[KansasCityWakeboard]

Hey I would pull off the muffler and see if a loose baffle is blocking the ports. That's what my 99 had going on last season and absolutely no one could figure it out until I'd eliminated all other possibilities. It was obvious as soon as I pulled the muffler and looked inside. Worn port hole marks on the baffle in front of both ports. Tho
My boat would run good to about 2700rpm under load. That was it. 3 repair shops gave up
You have to pull the upper exhaust manifolds to get the muffler off. It's easy
I just drilled holes in the baffle and then chewed peices out with a long needle nose pliers. Boat hit 5100rpm on first try after that.

[BallBushing]

Check your transmission cooler for debris. A clogged cooler will cause this. Happened to me.

[maristar225]

I never thought to really check them because I assumed they were pretty much holllow.

I will check them

[maristar225]

Took the hoses off the risers and ran it. and it does exactly the same. If we move the Throttle super super slow can get the RPMs up But go any faster than that it dies. This is hooked to a garden hose and in neutral. So the silencers aren’t the problem.

[igormaster]

valve springs?

check the compression on cylinders. Unplug one at at time and srew the compression tester in. any autoparts store would have one for under $15. if you have loss of compression on any one of the cylinders start with taking the valve cover off and visually check the valve springs. In most cases there will be no further damage... just replacing springs. No yanking of the engine necessary. With one or two broken springs the engine will run at idle but die under load. it happend on my 2011 ilmore twice on the same cylinder within one week .... just the bad batch. I don't know your engine but the symptoms are there .... and it should not be a dealer or mechanics trip.
igor

[maristar225]

Checked compression and all are 190-200. It is not loosing spark on any cylinders while it is dying. Earlier I checked that the injections were still getting pulsed while it was dying and it was, but I didnt check every single one. Next time I work on it I am going to check alll of them.

Any more ideas?

Could it be dirty fuel injectors?

If so do you suggest cleaning the old ones or buying new?