Which parts fail
Components named in complaints (engine, cooling system, oil leaks, timing chain, exhaust).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 1999 Pontiac Bonneville owners, lightly cleaned up (personal details are redacted by NHTSA).
While running, vehicle experienced a back fire causing the manifold to crack which caused a fire. Dealer notified. Ts when backfire occurred engine died and there was smoke from under the hood. Consumer was able to control the fire with snow. Referenced in ea02-030
1999 Bonneville; 58,000 miles; it had been stalling intermittently for several weeks -- especially during turns. Before I could take it to the dealer, the car loses power on hwy 63; fortunately, I was able to pull over. The mechanic reports engine has locked up because coolant has leaked into the engine due to a known problem by GM of coolant leaking into engine and thus destroying the engine. Total costs to replace the engine, the manifold and damaged the starter amounted to a repair bill of $5300 after a 10% existing customer discount plus state taxes. I checked the odi databases for '99 Bonneville's and almost a 1/3 of the 111 complaints relate to the same problems I had before my car engine was damaged and similar problems of coolant leaks into the engine. Does there have to be a injury before the NHTSA will act? …
I had to have the intake plenum replaced on my 99 Pontiac Bonneville...started with vehicle hesitating on take off, RPM's accelerating very high but MPH not catching up...vehicle then backfired and loss all power...had it towed to dealer...dealer said intake plenum was warped causing coolant to possibly leak into engine...GM would not cover under warranty which cost me $1000 to correct...vehicle was fine for a month or so and started doing it again. I think its ridiculous that GM knows about this problem but refuses to take responsibilty for it as a factory problem..I would like a recall on this and my money reimbursed to me. I also think this problem should be repaired correctly with a part that won't burn up because its made of plastic. I have read on many websites complaints about this same problem but the problem is that they are complaining to the wrong people. …
I've had major problems with my 99 Bonneville, costing me over $2,400. It started at 64,000 miles (6/26/02) with a backfire caused by a faulty fuel pressure regulator, which now has a service recall (a little too late); that cost me $300. A week later, the upper manifold plenum leaked causing the engine to flood and die; I spent over $500 on that little project (replacing the manifold and cleaning the engine). It never ran right after that; I had extremely low gas mileage and lack of power, and the engine light kept coming on and off and it stalled on many occasions. After about six months of this, it died again on 3/22/03. This time, it spun the main bearing and the lower half was ruined. I went to three different mechanics before I could find someone willing to touch it, but I found a good mechanic that rebuilt the lower half (versus replacing the engine) for $1,600. …
Plastic engine intake plenum assy meltdown causing coolant into cylinders of engine. Original incident identified to possible damage to 1st cylinder. Plenum assy replaced with metal sleeve which mechanic claimed was superior to original mfg part. Prior damage to 1st and 2nd cylinders became permanent months later when engine shutdown while driving. Researched recall data and found nothing to date. Mechanic acknowledges problem is frequent and known by manufacturer for long time. Contacted GM and was refused any type of compensation. Researched complaints on NHTSA a found an unbelievable large volume of the exact same problem. Intend to call NHTSA direct and find out status of large complaint base with no action. Intend to contact all others filing complaints for definite immediate class action.
Tl contact owns a 1999 Pontiac Bonneville. In 2003, while driving 15 MPH, the contact noticed a huge cloud of white smoke at the rear of the vehicle. The dealer stated that the intake manifold had blown the gasket. The intake manifold gasket was replaced as well as the intake manifold itself. In 2005, the fuel pressure regulator switch blew out and was repaired under recall; however, the failure recurred in 2007. The vehicle was taken to an independent mechanic and the contact was informed that this would cause the engine to blow due to leakage of fuel into the engine. Also, the rear window defroster switch would not shut off. He had to remove the fuse to prevent it from draining the battery. The failure mileage was 63,000 and current mileage was 104,000. Update 09/10/08 updated 09/19/08.
In mid May I had a authorized Pontiac dealer replace the intake manifold which had ruptured after a backfire upon initial start of 1999 Pontiac Bonneville with a 3.8 l engine. On June 1, 2004, I was nearly near ended on interstate 80 in council bluffs as I retruned from a trip because vehicle lost power. Took to dealer and they said lower bearing was gone, meaning a new engine. I know there have been numerous consumer complaints. It's more than the cost of a new engine that I'm concerned about. With my near incident that could have resulted in serious injury to me or another party, I think it's time that GM take responsibility for these issues and a recall is gone to cover the issue.
Upon accelerating onto the highway, after reaching highway speed, vehicle stalls and would not start. Flooding engine, gasoline coming out of exhaust, engine would not restart. After research and replacing leaking lower intake manifold, this was not my problem there was no leak. After more research I replaced more sensors and eventually cylinder gaskets and lower intake gasket again. Still engine would not start. After 2 years of car sitting I unplugged maf sensor and then it started finally. Faulty maf sensor but no way to find out unless it is unplugged because sensor did not give off any pertaining fault code pointing to the problem specifically.
I have a 1999 Pontiac Bonneville. The car would not start and I had it towed to dobbs. Dobbs investigated and found that the upper plenum had warped. Thereby causing the starter to fail and antifreeze to get into the engine. Pontiac knew about this problem and corrected it on the year 2000 model. However, they did not do a recall and left us poor saps to have to pay for the repairs ourselves. Since my car is out of warranty, they have said that it is my own problem. I am out of pocket $1,046.96 plus $40 towing fee for a problem they knew about and didn't recall. I wish to be reimbursed.
99 Bonneville, in March of 2004 while traveling at 45 MPH the car back fired and the engine killed, it was towed to a shop and coolant was in the engine. The upper manifold was replaced and gaskets at cost of over $ 600.00. A year later March 2005 the car was making a noise. The Pontiac dealer could not find a problem. On April 2005 the porblem was find, haha , plastic intake was crank, more money. I thing GM sould recall and pay a these defects in there parts. I will fight till the end. I have spent over 1000.00 on there defect, me many many other people.
NHTSA investigations
Engine compartment fires
Engine compartment fire
By letter dated March 12, 2008, general motors corp. (GM) has notified the agency that it will conduct a safety recall (identified by NHTSA recall number 08v-118) to address a defect in approximately 207,542 model year (my) 1997-2003 Buick regal gs and Pontiac grand prix gtp vehicles equipped with the l67 supercharged version of GM's 3800 series ii v6 engine.the recalled regal gs vehicles were built from August 1996…
Engine complaints in other Bonneville years
Frequently asked questions
How common are engine problems on the 1999 Pontiac Bonneville?
NHTSA has 60 complaints about the engine & cooling of the 1999 Pontiac Bonneville, 42% of the model year's 143 complaints. The component named most often is engine › gasoline (18 mentions).
Is there a recall for 1999 Pontiac Bonneville engine problems?
No. NHTSA lists no engine & cooling recall for the 1999 Pontiac Bonneville, though it has 3 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 1999 Pontiac Bonneville engine problems start?
Half of the complaints with a recorded mileage happened before about 65,000 miles, and 3% before 25,000 miles.
Is it dangerous?
Owners linked 1 crash, 5 fires and 0 injuries to engine & cooling problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.