LumiLTZ Posted September 21, 2013 Report Share Posted September 21, 2013 (edited) Drove my pewter '98 Lumina LTZ for the first time on the highway today since I got it back last weekend (all this week it's been just short trips to/from the train station, the store, etc). Anyhow, on the way home today, I was behind a slow car, and saw a good opening to overtake. I signal like a good driver does, then take it to WOT (I'm doing about 50-55 or so behind this slow car in the left lane, rest of traffic's probably doing 65-70) to quickly get up to the speed of the rest of traffic. As soon as I put the gas down (I try not to waste any time getting up to speed and I wasn't this time around as there was a pack of cars behind me reeling me in), the car kicks down (to 2nd I believe) but the car doesn't want to go. It starts bucking and kicking, as if I'm hitting the rev limiter...the tach was bouncing around 4k rpm, and the car felt like it was still in gear - when the engine revved back up each time I'd feel the car surge forward, on the rev-down it'd slow down, repeat as long as the car was in this state. I backed out of the gas a bit, and after getting back on it about 1/2 to 2/3 throttle it kicked down to 3rd just fine and I was able to make my pass, just a little slower than I'd like to...that pack of cars pretty much caught up to me by the time I got it to accelerate. Got off the highway at my usual exit and was first in line at a red light, so I did a WOT takeoff... and in 1st gear, once I got up to around 4k RPM, it started bucking/bouncing off the rev limiter/whatever again. Let off the gas, back on it about 1/2 to 3/4 throttle and it went into 2nd no problems and I got back on it hoping to see if it'd do it once I got up toward 4k RPM in 2nd, but I ended up catching up with traffic that was still getting moving at the next light by then so I had to get out of the throttle. Did a trans pan drop/fluid/filter change about 10k miles ago, also new plugs/wires this last weekend. No CEL lit, and no stored codes from what I gather hooking up a scan tool. Any thoughts? Seems as though the PCM is thinking the car's in neutral or something and not letting it rev above 4k RPM. Upshifts/downshifts seem fine at part throttle. This would be a 3800/4T65e car. Edited September 21, 2013 by LumiLTZ Quote Link to comment Share on other sites More sharing options...
Schurkey Posted September 21, 2013 Report Share Posted September 21, 2013 Fuel pressure at WFO? Quote Link to comment Share on other sites More sharing options...
LumiLTZ Posted September 21, 2013 Author Report Share Posted September 21, 2013 Fuel pressure at WFO? Haven't dug into it that far yet, but that's something on the list to check. I put in a new ACDelco fuel pump and replaced the fuel filter about 15k miles ago. The car just seems like it won't rev above 4k RPM, as if when it's in park. Quote Link to comment Share on other sites More sharing options...
AL Posted September 22, 2013 Report Share Posted September 22, 2013 Sounds like your cat is clogged, Ive seen this quite a few times Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted September 24, 2013 Report Share Posted September 24, 2013 i was going to say clogged cat too. Quote Link to comment Share on other sites More sharing options...
LumiLTZ Posted February 2, 2014 Author Report Share Posted February 2, 2014 Update... I haven't been seeing this as much with the car with the colder weather, though once in a while if I mash it to the floor to make a pass while on the highway (initial speed probably doing 50-55mph, TCC locked in OD) it acts as if it won't downshift and starts kicking/bucking. Let up on the gas and it will stop bucking and will downshift to 3rd, then give it more gas and it'll go to 2nd no problems and pull all the way through the revs till it shifts into 3rd again. Seems it really doesn't like kicking down from OD/4th to 2nd all at once. Quote Link to comment Share on other sites More sharing options...
ONCEBITN Posted February 2, 2014 Report Share Posted February 2, 2014 ive been doing alot of research on our trans and what im seeing is the shift solinods go bad Quote Link to comment Share on other sites More sharing options...
LumiLTZ Posted April 12, 2014 Author Report Share Posted April 12, 2014 Haven't really driven this car out on the highway the last couple months (either the wife's been driving it or when I've driven it it's just around town/to the train) but today I was out on the highway and it defintely felt like it was running with a 4k rev limiter as if in park/neutral. Car definitely is staying in whatever gear it is in at the time as it lurches/bucks as it bounces off that magic 4k RPM peg. I wonder, could there be something up with the park/neutral switch on the trans? Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted April 12, 2014 Report Share Posted April 12, 2014 Not likely te P/N switch. They are computer controler trans and wouldn't shift if it thought it was in P/N. still think clogged cat. But could be a shift solenoid or tw converter problem. Are there any check engine lights? Quote Link to comment Share on other sites More sharing options...
LumiLTZ Posted April 13, 2014 Author Report Share Posted April 13, 2014 No CEL on currently or any stored codes. just an intermittent bogus low coolant light. Any checks I can do to confirm a clogged cat? Quote Link to comment Share on other sites More sharing options...
Nas Escobar Posted April 13, 2014 Report Share Posted April 13, 2014 Easiest way would be to separate the cat out of the exhaust tubing and see if it still does it. I personally want to say that it's the TCC switch or shift solenoid switch, but that's just a guess like the clogged cat. Quote Link to comment Share on other sites More sharing options...
LumiLTZ Posted April 13, 2014 Author Report Share Posted April 13, 2014 Been doing some research as well on checking for a clogged cat... looks like I can use a vacuum gauge as follows: 1. Connect a vacuum gauge to a vacuum line fitting on the intake manifold. The easiest access points are either off the vacuum fitting going to the brake booster check valve or the vacuum hose fitting for the charcoal canister purge valve. 2. Record vacuum at idle (usually over 17 inches of Hg). 3. Record vacuum at 3000 RPM with engine at no load. 4. The vacuum reading taken in step 3 should be at least as great as that taken in step 2. If the vacuum reading in step 3 starts dropping (even going positive) from it original reading, then you could have a clogged converter. I have a vacuum gauge so I'm gonna try that tomorrow and see what I come up with. Quote Link to comment Share on other sites More sharing options...
Nas Escobar Posted April 13, 2014 Report Share Posted April 13, 2014 Hmmm that's actually a good idea LumiLTZ. I never knew you could do that. Quote Link to comment Share on other sites More sharing options...
LumiLTZ Posted April 23, 2014 Author Report Share Posted April 23, 2014 Got a chance to mess with this thing this afternoon after work. Checked fuel pressure, have 50PSI key on, engine off. 42psi at idle. Pulled vac line off the regulator and it climbed right back to and stayed at 50psi. Also did the vacuum gauge test, pulls 20" vacuum at idle, revving up to 3k RPM and holding it there for 1 minute, vacuum quickly recovered to and remained right around 22". Anyone got the specs of what my fuel pressure should be on this car? Quote Link to comment Share on other sites More sharing options...
LumiLTZ Posted May 3, 2014 Author Report Share Posted May 3, 2014 Decided to try a few things with swapping parts from the wife's Lumina onto mine... swapped coils/ICM to no effect the other day, and then yesterday I stole the MAF sensor off it. Drove the car on the highway today and it showed no problems punching it at 55mph. Kicked down and pulled to over 5k before shifting up trouble-free and doing 75mph. With the other MAF it wasn't ever throwing any codes, and I'd replaced it about a year ago with a Delphi after it did set a code and I was having unstable idle/stalling issues. The one from the wife's Lumina is an OE Hitachi AFH50M-04. So looks like it's the MAF making it act up. Quote Link to comment Share on other sites More sharing options...
Psych0matt Posted May 4, 2014 Report Share Posted May 4, 2014 I don't think the luminas were ever meant to accelerate that fast, so no one has ever had this issue before... Quote Link to comment Share on other sites More sharing options...
LumiLTZ Posted May 4, 2014 Author Report Share Posted May 4, 2014 Probably not, and mine was owned by some old guy before I bought it, but when I'm on the highway stuck behind a Prius doing below the speed limit in the left lane, it calls for driving it like it's a GP. Quote Link to comment Share on other sites More sharing options...
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